Obsessive-compulsive Disorder
Obsessive-compulsive disorder is a chronic psychiatric condition characterized by intrusive, unwanted thoughts (obsessions) and repetitive behaviors or mental acts (compulsions) performed to reduce the resulting anxiety.
Obsessive-Compulsive Disorder (OCD) — let's break the name down:
- "Obsessive" → from Latin obsidēre = "to besiege" — the mind is besieged by intrusive, unwanted thoughts
- "Compulsive" → from Latin compellere = "to drive, to force" — the person feels driven to perform repetitive behaviours
- "Disorder" → this crosses the threshold from normal quirks into clinically significant distress or functional impairment
OCD is a chronic neuropsychiatric disorder characterised by the presence of obsessions (recurrent, intrusive, unwanted thoughts, images, or urges) and/or compulsions (repetitive, stereotyped behaviours or mental acts performed in response to obsessions or according to rigid rules), which are:
- Recognised as arising from the patient's own mind (not inserted from outside — this distinguishes it from thought insertion in psychosis) [1][2]
- Associated with a sense of compulsion — the patient cannot control them despite wanting to [1][2]
- Associated with a sense of resistance — the patient tries to resist them (though this may diminish over time as the illness becomes chronic) [1][2]
- Ego-dystonic — in conflict with the patient's own values, goals, and self-concept; recognised as senseless or excessive [1][2]
Key Defining Features — Mnemonic: 'CORE'
C — Compulsion (sense of being driven, cannot control) O — Own thoughts (recognised as originating from self) R — Resistance (attempts to resist, though may wane) E — Ego-dystonic (recognised as senseless, in conflict with self)
OCD vs OCPD — A Common Exam Trap
Do NOT confuse OCD with Obsessive-Compulsive Personality Disorder (OCPD/Anankastic PD). In OCPD, the traits are ego-syntonic (the person sees their rigidity and perfectionism as reasonable and desirable). In OCD, the obsessions and compulsions are ego-dystonic (the person recognises them as irrational and distressing). Furthermore, OCPD does not have ritualistic compulsions in the way OCD does. Although OCPD is over-represented in OCD patients (~23–32%), people with OCPD are actually more likely to develop depression than OCD [3].
2. Epidemiology
| Parameter | Detail |
|---|---|
| Prevalence | ~2% of the general population (12-month prevalence ~1.2%, lifetime prevalence ~2.3%) [1][4] |
| Mean age of onset | 19.5 years, with 25% starting by age 14 [1][4] |
| Sex ratio | Female : Male ≈ 1:1 in adults (lecture slides state 1:1); senior notes cite some studies showing F > M ≈ 1.2–3.8:1 — the discrepancy reflects study methodology. However, males have earlier onset than females [4] |
| Childhood OCD | M > F; earlier onset in boys is a consistent finding |
| Course | Typically gradual onset; rarely remits spontaneously (~20% in 40 years) if untreated [3] |
| Prognosis | ~2/3 improve to some extent within 1 year of treatment; ~40% remission at 15 years [3] |
| Better Prognosis | Worse Prognosis |
|---|---|
| Identifiable precipitating event | Childhood onset |
| Good premorbid adjustment | Personality disorder |
| Episodic symptoms | Tic-related OCD |
| Male sex | |
| Overvalued ideas about obsessions (poor insight) | |
| Comorbid depression |
This is extremely high-yield — OCD is almost never alone:
| Comorbidity | Prevalence |
|---|---|
| > 70% lifetime diagnosis of an anxiety disorder (panic disorder, social anxiety disorder, GAD, specific phobia) | ~76% |
| > 60% lifetime diagnosis of a mood disorder — MDD being the most common (~41%) | ~63% |
| OC personality disorder | 23–32% |
| Up to 30% lifetime tic disorder | Up to 30% |
| 12% of persons with schizophrenia/schizoaffective disorder | 12% |
| Others | Bipolar disorder, eating disorders, substance use disorders |
Why the High Comorbidity with Depression?
The chronic, distressing, ego-dystonic nature of obsessions leads to demoralisation, helplessness, and functional impairment → secondary depression is extremely common. Additionally, shared serotonergic dysfunction may predispose to both conditions. When both OCD and depression are present, the ICD-10 advises giving diagnostic precedence to whichever developed first [3].
3. Anatomy and Neurocircuitry
Understanding the neuroanatomy is essential because OCD, unlike many other psychiatric disorders, has a relatively well-defined circuit abnormality. This is one of the most testable aspects of OCD.
The orbitofrontal cortico-striato-thalamo-cortical (CSTC) circuit dysfunction is widely cited as the major abnormality underpinning OCD [1][3].
How does this loop normally work?
The CSTC loops are parallel circuits that connect cortical areas → striatum (basal ganglia) → thalamus → back to the same cortical area. They exist for motor, cognitive, limbic and other functions. The orbitofrontal CSTC loop specifically handles:
- Decision-making about whether an action is "complete" or requires repetition
- Habit learning vs. goal-directed behaviour — the OFC mediates the balance between compulsivity (tendency toward habitual/routine behaviour) and impulsivity (tendency toward reward-driven/goal-directed behaviour) [3]
- Error monitoring — "Have I done this correctly? Is there danger?"
What goes wrong in OCD?
OCD arises from a hyperactive orbitofrontal CSTC loop [3]:
- The OFC fires excessively → generates a persistent feeling that "something is wrong" or "incomplete"
- This hyperactivity propagates through the caudate → thalamus → back to the OFC
- The result is a self-reinforcing loop: the brain keeps signalling danger/incompleteness, driving the person to check, wash, count, etc.
- Performing the compulsion provides temporary relief (the loop briefly quiets), but this negatively reinforces the cycle
| Structure | Imaging Finding | Functional Role in OCD |
|---|---|---|
| Orbitofrontal cortex (OFC) | ↑ activity on functional imaging; ↓ grey matter volume | Error detection, "something is wrong" signal |
| Caudate nucleus (striatum) | ↑ activity; ↑ grey matter volume | Gating of habitual behaviours; normally filters out irrelevant thoughts |
| Anterior cingulate cortex (ACC) | ↑ activity; ↓ grey matter volume in dorsomedial and anterior portions | Conflict monitoring; detects discrepancy between intended and actual state |
| Thalamus | ↑ activity | Relay centre; when hyperactive, fails to filter out repetitive signals |
Structural imaging summary: ↑ grey matter volume in striatum, ↓ grey matter in OFC, dorsomedial and anterior cingulate cortex [3].
Functional imaging summary: ↑ activity in OFC, caudate, ACC, and thalamus — all key nodes of the CSTC loop [3].
3.3 Neurotransmitter Systems
Studies implicate a role for abnormalities in 5-HT function [1][3]:
- Serotonergic agents (e.g., SSRIs) are effective in treating OCD — this was historically the strongest evidence for serotonin involvement
- OCD requires higher doses of SSRIs and longer duration to respond compared to depression (typically 8–12 weeks vs. 4–6 weeks) — this suggests the mechanism is different from simply correcting a serotonin deficit
- However, studies attempting to confirm 5-HT abnormalities in the brain have been inconsistent [3]
- ↓ cortical 5-HT1A binding has been described
- Glutamate transporter gene (SLC1A1) is the most consistently replicated genetic finding in OCD [3]
- The CSTC loop uses glutamate as its primary excitatory neurotransmitter
- Glutamate excess in the striatum could drive the hyperactive loop
- This has led to interest in glutamate-modulating agents (e.g., memantine, riluzole, N-acetylcysteine) as adjunctive treatments
- Tic-related OCD and OCD with poor insight may involve dopaminergic pathways
- This is why antipsychotics (dopamine blockers) are used as augmentation in treatment-resistant OCD
4. Aetiology
4.1 Biological Factors
- Genes are thought to play a significant role, more so in paediatric-onset cases [3]
- Family studies: MZ > DZ concordance rate; first-degree relatives have 4× risk [3]
- Candidate genes [3]:
- Glutamate transporter (SLC1A1) — most consistently replicated
- Serotonin transporter (5-HTTLPR)
- 5-HT2A receptor gene
- BDNF gene (brain-derived neurotrophic factor) — not consistently replicated
OCD is associated with several brain disorders that give us clues about pathophysiology:
| Condition | Relevance |
|---|---|
| Encephalitis lethargica | An atypical encephalitis of unknown origin (postulated to be post-influenza) that frequently presents with OC symptoms; demonstrates that basal ganglia pathology → OCD-like symptoms [3] |
| Tourette's syndrome | OC symptoms were once included in diagnostic criteria; up to 30% of OCD patients have tics; shared striatal pathology [3] |
| PANDAS | Paediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal infection — 70% of Sydenham's chorea (which affects the caudate nucleus) has OC symptoms; anti-basal ganglia antibodies from molecular mimicry cross-react with striatal neurons [1][3] |
Why PANDAS Matters
PANDAS elegantly demonstrates the neurobiological basis of OCD. Group A streptococcal infection triggers an autoimmune response → antibodies cross-react with the caudate nucleus (molecular mimicry) → caudate dysfunction → OC symptoms. This is the same caudate nucleus that is hyperactive in the CSTC loop model. The fact that treating the autoimmune process can resolve OCD symptoms in these children is powerful evidence for a neurobiological basis.
As discussed above — SSRIs work, but the exact serotonin abnormality remains inconsistent across studies. The serotonin hypothesis is probably an oversimplification; serotonin likely modulates the CSTC loop rather than being the primary "cause."
4.2 Psychological Factors
- Associated with obsessive-compulsive personality (anankastic traits: orderliness, perfectionism, rigidity)
- But remember: ~1/3 of OCD patients have other personality types, and people with OCPD are actually more likely to develop depression than OCD [3]
OCD is explained as an inability to control normal intrusive impulses and see them in perspective [3]:
- Everyone has intrusive thoughts — studies show that 80–90% of the general population experiences intrusive thoughts similar in content to clinical obsessions (e.g., "What if I push this person onto the train tracks?")
- The difference in OCD is how these thoughts are appraised:
- OCD patients respond to intrusive thoughts as if they were personally responsible for their possible consequences [3]
- e.g., thinking "What if I harm my child?" → the OCD patient interprets this as "I am a dangerous person and I might actually do it"
- This feeling of responsibility → excessive attempts to ward off the thoughts and their supposed consequences [3]
- These attempts take the form of:
- Compulsive behaviours (checking, washing, counting)
- Avoidance (avoiding triggers)
- Reassurance-seeking (repeatedly asking others for confirmation of safety)
- The compulsions temporarily reduce anxiety → negative reinforcement → the cycle is maintained
This cognitive model is the basis for Cognitive Behavioural Therapy (CBT) with Exposure and Response Prevention (ERP).
| Factor | Detail |
|---|---|
| Stressors | Acute onset OCD has been reported following exposure to traumatic events [3] |
| Hormonal fluctuations | Premenstrual and postpartum periods can lead to new onset or exacerbation of OCD, suggesting that hormonal fluctuations may play an aetiological role [3] |
| Childhood adversity | Neglect, abuse may contribute as non-specific risk factors |
5. Classification
In the ICD-11 (2019, adopted progressively), OCD has been removed from the anxiety disorders and placed in its own category: "Obsessive-Compulsive and Related Disorders (OCRDs)". This reflects the understanding that while anxiety is prominent in OCD, the core pathology (CSTC loop dysfunction, compulsivity) is distinct from primary anxiety disorders.
The OCRD category includes:
- Obsessive-Compulsive Disorder
- Body Dysmorphic Disorder (BDD)
- Hoarding Disorder
- Trichotillomania (hair-pulling disorder)
- Excoriation Disorder (skin-picking disorder)
- Olfactory Reference Disorder (new in ICD-11)
- Hypochondriasis (illness anxiety disorder — placed here in ICD-11 but under somatic symptom disorders in DSM-5)
Similarly in DSM-5 (2013), OCD was moved out of anxiety disorders into "Obsessive-Compulsive and Related Disorders".
| Specifier | Description |
|---|---|
| With good or fair insight | Recognises that OCD beliefs are definitely or probably not true |
| With poor insight | Thinks OCD beliefs are probably true |
| With absent insight/delusional beliefs | Completely convinced OCD beliefs are true — this is the most treatment-resistant subtype |
| Tic-related | Current or past history of a tic disorder — has treatment implications (may benefit from antipsychotic augmentation) |
This is a clinically useful way to categorize OCD presentations. The four major dimensions are:
| Dimension | Obsession Content | Compulsion |
|---|---|---|
| Contamination/Cleaning | Fear of contamination by dirt, germs, faeces, bodily fluids, chemicals | Excessive handwashing, cleaning rituals, avoidance of "contaminated" objects |
| Doubt/Checking | Uncertainty about previous actions (e.g., "Did I lock the door?" "Did I turn off the stove?") | Excessive checking rituals |
| Symmetry/Ordering | Need for symmetry, precision, "just right" feeling | Repeated rearrangement, counting in particular patterns |
| Forbidden thoughts | Aggressive impulses, blasphemous thoughts, sexual obsessions | Avoidance of objects associated with violence; acts of redemption (e.g., repeating "forgive me" 15 times); reassurance-seeking from the "victim" |
Hoarding — No Longer Under OCD
Hoarding was previously considered a subtype of OCD but is now a separate diagnosis in both DSM-5 and ICD-11. Unlike classical OCD, hoarding is typically ego-syntonic (patients see value in their possessions and resist discarding them), and it does not respond well to SSRIs or standard OCD treatments.
6. Clinical Features
6.1 Symptoms (Subjective — What the Patient Reports)
Obsessions are recurrent, intrusive thoughts, impulses, images, ruminations, or doubts that are unwanted and cause marked anxiety or distress [1][2].
| Type | Description | Example | Pathophysiological Basis |
|---|---|---|---|
| Obsessional ruminations | Internal debates with arguments for and against everyday actions, reviewed endlessly | "Did I wash my hands properly? What if there are still germs?" | Hyperactive OFC error-detection circuit generates persistent "incomplete" signals → the patient cannot experience a sense of completion |
| Obsessional impulses | Urges to perform acts, usually of a violent or embarrassing kind | Urge to leap in front of a car; urge to shout obscenities in church | Normal intrusive impulses (which everyone has) are catastrophically misappraised due to inflated sense of responsibility → excessive anxiety about acting on them |
| Obsessional images | Vivid mental pictures, often of a violent or sexual nature | Images of harming one's child | Amygdala activation by the emotionally charged content → anxiety → reinforces the obsessional cycle |
| Obsessional doubts | Persistent uncertainty about whether an action was completed | "Did I lock the door? Did I turn off the gas?" | Caudate nucleus normally signals task completion; caudate dysfunction → failure to generate the "done" signal |
| Obsessional phobias | Worsening of OC symptoms in certain situations, leading to avoidance | Person with violent impulses avoids the kitchen where knives are kept | Contextual cues activate the CSTC loop → increased obsessional activity → avoidance is adopted as a maladaptive coping strategy |
Key themes of obsessions (from lecture slides): dirt, contamination, aggression, illness, religion [2]
Compulsions are repetitive, stereotyped behaviours or mental acts performed to reduce the anxiety caused by obsessions or to prevent a dreaded event [1][2].
| Type | Description | Example | Pathophysiological Basis |
|---|---|---|---|
| Compulsive checking | Repeated verification of actions | Checking locks, stove, taps multiple times | Caudate dysfunction → cannot register task as "complete" → repeated checking attempts to generate the missing "done" signal |
| Compulsive cleaning | Excessive washing or cleaning rituals | Handwashing for 30 minutes until skin is raw | Contamination obsession triggers anxiety → cleaning temporarily reduces anxiety (negative reinforcement) → OFC circuit briefly quiets → anxiety returns → cycle repeats |
| Compulsive counting | Counting in specific patterns or to specific numbers | Must count to 7 before entering a room | Ritualistic attempt to impose order/control on the "incomplete" signal; may be tied to magical thinking |
| Obsessional slowness | Slowness not explained by time consumed by obsessive rituals — can be considered an obsession in itself | Taking 3 hours to get dressed because every step must be done "perfectly" | Hyperactive error-monitoring (ACC/OFC) → each sub-step must be evaluated for correctness → extreme slowing |
| Mental rituals | Covert cognitive acts (praying, counting silently, repeating phrases) | Silently repeating "forgive me" 15 times after a blasphemous thought | Functionally equivalent to overt compulsions but harder to detect clinically |
Key types of compulsions (from lecture slides): checking, cleaning, counting, slowness [2]
The Obsession-Compulsion Relationship
Not all obsessions have paired compulsions, and vice versa. Some patients have predominantly obsessional symptoms (ICD-10 F42.0) or predominantly compulsive symptoms (F42.1), or mixed (F42.2). However, the vast majority (~90%) have both. Even patients who deny compulsions often have mental rituals that function as compulsions.
OCD is largely a disorder of subjective experience, so signs on examination are relatively few compared to symptoms. However, astute observation can reveal:
| Sign | Observation | Pathophysiological Basis |
|---|---|---|
| Dermatitis / excoriation of hands | Red, cracked, raw skin on hands and forearms | Excessive handwashing compulsions → mechanical and chemical damage to skin barrier |
| Skin picking / hair pulling | Focal alopecia (trichotillomania), excoriated lesions | OC-spectrum behaviours; may represent a compulsion to achieve a "just right" feeling |
| Avoidance behaviours | Patient may refuse to touch certain objects, sit in certain areas, or use public facilities | Contamination obsessions → avoidance of perceived triggers |
| Ritualistic behaviours during consultation | Repetitive touching, tapping, rearranging objects, checking | Observable compulsions; the patient may feel compelled to perform rituals even in the clinic |
| Slowness | Taking unusually long to complete simple tasks (e.g., filling in a form) | Obsessional slowness — each action must meet a perfectionistic standard |
| Distress and anxiety | Visible tension, sweating, restlessness, tearfulness when unable to perform rituals | Anxiety is the primary affective response to obsessions; blocking compulsions acutely increases anxiety |
| Low mood / flat affect | Secondary to chronic illness and demoralisation | Comorbid depression (>60%); also, the exhausting nature of constant obsessions erodes mood |
| Depersonalization | Patient may report feeling detached from self | Sometimes reported in OCD; relationship with OC symptoms is unclear [3] |
6.3 Associated Features [3]
- Avoidance behaviour: patients often avoid cues that trigger OC symptoms (e.g., individuals with contamination concerns avoid public situations) — this may become pervasive and severely restrict functioning [3]
- This is critically important for prognosis and treatment planning:
- Good insight → better treatment response (especially to CBT)
- Poor insight / overvalued ideas → worse prognosis; may border on delusional
- Absent insight / delusional beliefs → most treatment-resistant; may require antipsychotic augmentation
The lecture slides emphasize that OCD patients typically maintain insight and regard their symptoms as senseless [2]. This is a hallmark distinguishing OCD from psychotic disorders — the patient recognises "I know this is irrational, but I can't stop." Over time, however, insight may diminish.
The lecture slides specifically highlight resistance as a key clinical feature [2]. The patient actively tries to resist the obsessions and compulsions. This is characteristic of OCD — in contrast to, say, impulsive behaviours in personality disorders where there may be less resistance.
(Full differential will be covered in the next section, but briefly for context:)
| Differential | Key Distinguishing Feature |
|---|---|
| Normal intrusive thoughts | Present in 80–90% of population but do NOT cause distress, are easily dismissed, do not lead to compulsions |
| Generalised Anxiety Disorder (GAD) | Worries in GAD are about real-life concerns (finances, health) and are ego-syntonic; in OCD, obsessions are ego-dystonic and often bizarre/irrational |
| Depressive rumination | Mood-congruent, focused on past failures/guilt; lacks the repetitive ritualistic quality of OCD |
| Psychosis / Schizophrenia | Thought insertion (thoughts feel alien, placed by external force) vs. OCD (thoughts recognised as own); in OCD with absent insight, this distinction can be challenging |
| Obsessive-Compulsive Personality Disorder (OCPD) | Ego-syntonic traits (perfectionism, orderliness felt as appropriate); no true obsessions or compulsions |
| Tic disorders | Simple, brief, non-purposeful motor or vocal tics vs. complex, purposeful compulsions; but can co-occur |
| Body Dysmorphic Disorder (BDD) | Preoccupation specifically with perceived physical appearance defects; classified under OC-related disorders [3] |
| Organic causes | Encephalitis lethargica, Tourette's, PANDAS, Huntington's, basal ganglia lesions, frontal lobe lesions [3] |
The key insight is that OCD is a self-reinforcing loop at both the neural level (CSTC circuit) and the behavioural level (obsession → anxiety → compulsion → relief → obsession). Treatment must break this loop at one or more points — pharmacologically (SSRIs modulate serotonin in the CSTC circuit) and/or behaviourally (ERP prevents the relief step, allowing habituation).
High Yield Summary
- Definition: Obsessions ± compulsions that are CORE — Compulsion (driven), Own thoughts, Resistance, Ego-dystonic
- Epidemiology: ~2% prevalence; mean onset 19.5y; 25% by age 14; M=F in adults but M earlier onset; rarely remits untreated (~20% in 40y)
- Comorbidities: > 70% anxiety disorders; > 60% mood disorders (MDD most common); up to 30% tic disorders; 12% schizophrenia/schizoaffective
- Neurocircuitry: Hyperactive orbitofrontal CSTC loop (OFC → caudate → thalamus → OFC); ↑ activity in OFC, caudate, ACC, thalamus on functional imaging
- Aetiology: Genetics (SLC1A1 glutamate transporter most consistent), serotonergic dysfunction, CSTC loop, PANDAS (autoimmune), cognitive factors (inflated responsibility), stress/hormonal triggers
- Clinical Features: Obsessions (ruminations, impulses, images, doubts, phobias) and compulsions (checking, cleaning, counting, slowness, mental rituals); maintained insight; presence of resistance; anxiety as primary affective response; avoidance behaviour; frequent comorbid depression
- Key distinction from OCPD: OCD = ego-dystonic, ritualistic compulsions; OCPD = ego-syntonic, perfectionism without true obsessions/compulsions
- Prognostic factors: Worse with childhood onset, tic-related, male, poor insight/overvalued ideas, comorbid depression, personality disorder
Active Recall - Obsessive-Compulsive Disorder (Definition, Epidemiology, Aetiology, Clinical Features)
[1] Lecture slides: GC 171. Stress-related disorders and obsessive-compulsive disorder (Post-traumatic stress disorder adjustment disorder, acute stress disorder)_rev.pdf (p37–39) [2] Lecture slides: GC 167. I feel very nervous Anxiety disorders.pdf (p31) [3] Senior notes: ryanho-psych.md (Section 8.2 Obsessive-Compulsive Disorder, pp. 186–190) [4] Lecture slides: GC 171 (p37) — Epidemiology of OCD [5] Lecture slides: GC 171 (p38) — Co-morbidities of OCD
Differential Diagnosis of OCD
The differential diagnosis of OCD is one of the trickiest areas in psychiatry exams because obsessions, compulsions, repetitive thoughts, avoidance, and anxiety are features shared across many disorders. The key to navigating this is to understand why each mimicker looks like OCD and what specific feature distinguishes it. Let's work through this systematically from first principles.
Before diving in, remember the psychiatric diagnostic hierarchy [6]. OCD sits in the "anxiety/neurotic" tier. When OC symptoms occur in the context of a higher-order disorder (organic, psychotic, mood), the ICD-10 convention is to attribute them to that higher-order condition rather than diagnosing comorbid OCD — unless the OC symptoms are clearly independent.
The higher the tier, the more likely it "explains away" the OC symptoms. Always rule out from the top down: organic → psychotic → mood → primary OCD.
| Differential | Key Shared Feature with OCD | How to Distinguish — Why It's Different | Pathophysiological Rationale |
|---|---|---|---|
| 1. Anxiety Disorders (GAD, Panic Disorder, Social Anxiety, Phobias) | Recurrent worries/ruminations, avoidance behaviour, prominent anxiety [3][7] | Content of ruminations in GAD tends to be related to real-life concerns (finances, health, family) — these are ego-syntonic worries about plausible outcomes. In OCD, obsessions are ego-dystonic, odd, irrational, or magical [3]. Compulsions are typically present in OCD but absent in pure anxiety disorders. GAD checking is directly related to the feared outcome and not excessive or ritualistic, whereas OCD compulsions are ritualistic/rule-driven and may be unrelated to the feared outcome or clearly excessive [7] | GAD involves hyperactivation of the worry circuit (prefrontal-amygdala), whereas OCD involves the CSTC loop (OFC-caudate-thalamus). The "error signal" in OCD is fundamentally different from the future-oriented threat appraisal in GAD |
| 2. Depressive Disorder | Ruminations, guilt, poor concentration, avoidance, functional impairment [3] | Ruminations in depression tend to be mood-congruent (focused on past failures, guilt, worthlessness) and not necessarily experienced as intrusive or distressing in the way OCD obsessions are. There is no compulsion associated with depressive rumination [3]. Depression and OCD frequently co-exist — when both are present, ICD-10 advises giving precedence to whichever developed first [3] | Depressive rumination involves the default mode network (medial PFC, posterior cingulate) — self-referential processing about past events. OCD obsessions involve the OFC error-detection circuit — a sense of "incompleteness" or danger requiring action (compulsion) |
| 3. Psychotic Disorders (Schizophrenia / Schizoaffective) | Bizarre, irrational beliefs; repetitive behaviours; poor insight in some OCD patients [3] | Some obsessions may resemble delusions due to oddity of beliefs or compulsive behaviours and weak resistance [3]. Key distinctions: (a) In OCD, thoughts are recognised as the patient's own — in schizophrenia, thought insertion/broadcasting means thoughts feel alien, inserted by an external force. (b) In OCD, even with poor insight, patients typically show some ambivalence; in psychosis, delusions are held with absolute conviction. (c) OC symptoms are common in schizophrenia (~12%) — actively elicit other psychotic features (hallucinations, thought disorder, negative symptoms) [3][5] | In schizophrenia, dopaminergic hyperactivity in mesolimbic pathways drives delusions. OCD involves serotonergic/glutamatergic dysfunction in the CSTC loop. However, there is overlap: the caudate is implicated in both, which may explain why OC symptoms frequently co-occur with schizophrenia |
| 4. Obsessive-Compulsive Personality Disorder (OCPD / Anankastic PD) | Preoccupation with orderliness, perfectionism, rigidity, need for control [3][6] | OCPD traits are ego-syntonic — the patient sees perfectionism and rigidity as reasonable and desirable. OCD symptoms are ego-dystonic — recognised as senseless and distressing. OCPD has no true ritualistic compulsions; behaviour reflects personality style, not anxiety-driven rituals. OCPD has no urge to perform ritualistic actions unlike OCD [6]. Note: OCPD is over-represented in OCD (23–32%), but people with OCPD are more likely to develop depression than OCD [3] | OCPD reflects stable personality traits (likely related to frontal lobe structure and temperament). OCD is an episodic illness driven by circuit-level dysfunction (CSTC loop hyperactivity). The trait-state distinction is key |
| 5. Other OC-Related Disorders | Repetitive behaviours, distress, compulsive quality [3][1] | Body Dysmorphic Disorder (BDD): OC symptoms are limited to concerns about physical appearance — preoccupation with perceived defects in appearance, mirror checking, camouflaging [3][8]. Trichotillomania: compulsive behaviour limited to hair-pulling, with no obsessions [3]. Hoarding Disorder: focus exclusively on persistent difficulty in discarding or parting with possessions — OCD should only be diagnosed when hoarding arises from typical OCD obsessions (e.g., incompleteness, fear of harm) [3]. Excoriation Disorder: compulsive skin picking without the broader obsessional content of OCD [1] | These OC-related disorders share some CSTC loop dysfunction with OCD but involve different cortical regions or different dimensions of compulsivity. BDD involves abnormal visual processing circuits; trichotillomania involves motor habit circuits (putamen > caudate); hoarding involves ventromedial PFC decision-making circuits |
| 6. Tic Disorders / Tourette's Syndrome | Repetitive motor or vocal behaviours [3] | Tics are typically less complex than compulsions and not aimed at neutralizing obsessions [3]. Tics are preceded by premonitory sensory urges (a physical sensation of tension in a body part) rather than obsessions (a cognitive experience). Tics are semi-voluntary — can be suppressed briefly but build up tension. Tic disorders may co-occur with OCD (up to 30%) [3][5] — when they do, this is specified as "tic-related" OCD, which has treatment implications (may benefit from antipsychotic augmentation) | Both involve basal ganglia (striatal) dysfunction. Tics primarily involve the sensorimotor CSTC loop (involving putamen), whereas OCD involves the orbitofrontal CSTC loop (involving caudate). Shared striatal pathology explains the high comorbidity |
| 7. PTSD / Acute Stress Disorder | Intrusive, recurrent thoughts; avoidance behaviour; hyperarousal [9] | In OCD, recurrent intrusive thoughts are unrelated to a traumatic event; in PTSD, intrusions are specifically related to the trauma (flashbacks, nightmares of the event) [9]. PTSD has a clear temporal relationship to a specific traumatic stressor, plus characteristic re-experiencing, avoidance of trauma-related stimuli, negative cognitions, and hyperarousal. Note: acute stress can precipitate OCD onset, but the OC content is typically not a re-experiencing of the traumatic event itself | PTSD involves amygdala hyperactivity with hippocampal-medial PFC dysregulation (failure to contextualize the trauma memory). OCD involves CSTC loop dysfunction. Different circuits, different content |
| 8. Eating Disorders (Anorexia Nervosa) | Ritualistic behaviours around food, body checking, preoccupation with weight/shape [10] | Both AN and OCD may have obsessional thoughts about food, body image, and ritualistic eating behaviours. However, in AN the core psychopathology is overvaluation of weight and shape with ego-syntonic dietary restriction (the patient wants to lose weight). In OCD, food-related obsessions are ego-dystonic (e.g., fear of contamination of food). OCD comorbidity is common in AN (~33%) [10] | AN involves dysregulation of reward circuits (ventral striatum, insula) related to body image, whereas OCD involves CSTC error-detection circuits |
| 9. Hypochondriasis / Illness Anxiety Disorder | Health-related preoccupations, checking behaviours, reassurance-seeking [11] | In hypochondriasis, the concern is principally about having a serious illness — it is a persistent fear/conviction of illness, not an intrusive unwanted thought. The patient seeks diagnosis rather than relief from intrusive thoughts. In OCD, health concerns are typically contamination-related (fear of getting contaminated → washing) and are accompanied by ritualistic compulsions [11] | Hypochondriasis may involve anterior insula (interoceptive processing) and threat-appraisal circuits, whereas OCD contamination obsessions are driven by the CSTC error-detection loop |
| 10. Organic Causes | OC symptoms arising from identifiable neurological/medical pathology [3] | OC symptoms may occur in chronic cases of encephalitis lethargica [3]; also seen with Tourette's syndrome, PANDAS, Huntington's disease, basal ganglia lesions (stroke, tumour), frontal lobe lesions, temporal lobe epilepsy, post-head injury. Always consider organic aetiology when: (a) onset is acute/atypical; (b) age > 40 at first presentation; (c) associated neurological signs; (d) poor response to standard treatment | Any process that disrupts the CSTC loop components (caudate, OFC, thalamus) can produce OC symptoms. PANDAS demonstrates this via autoimmune caudate inflammation; Huntington's via caudate atrophy; encephalitis lethargica via basal ganglia inflammation |
| 11. Substance-Induced | Anxiety, repetitive behaviours, agitation | Stimulant intoxication (amphetamines, cocaine) can cause repetitive stereotyped behaviours ("punding"). Withdrawal from sedatives/alcohol can cause anxiety resembling OCD. The key is temporal relationship to substance use — symptoms should resolve with cessation. Always take a thorough substance history [12] | Stimulants cause dopaminergic hyperactivity in striatal circuits → stereotyped behaviours that superficially resemble compulsions but lack the cognitive obsessional component |
| 12. Autism Spectrum Disorder (ASD) | Repetitive, stereotyped behaviours; insistence on sameness; rigid routines [13] | In ASD, repetitive behaviours are typically ego-syntonic (enjoyed or comforting), not driven by anxiety or intrusive thoughts. ASD has core deficits in social communication and reciprocity that are absent in OCD. Restricted interests in ASD are often pleasurable (e.g., intense fascination with trains), whereas OCD obsessions are distressing. However, OCD can co-occur with ASD | ASD involves widespread neurodevelopmental differences (cortical connectivity, mirror neuron system, etc.) whereas OCD is a circuit-specific disorder (CSTC loop) |
Detailed Discussion of the Most Commonly Tested Differentials
This is the single most commonly tested differential in exams. Here is how to think about it from first principles:
- GAD = the brain's threat-detection system is set too sensitively for real-world concerns. The worry is about things that could plausibly happen — "Will I lose my job? Will my child get sick? Can I pay the mortgage?" These worries are ego-syntonic — the patient thinks it is reasonable to worry about these things.
- OCD = the brain's error-detection/completion circuit (CSTC loop) fires excessively, generating a sense that "something is wrong" about irrational, bizarre, or magical themes. The patient knows the worry is senseless but cannot stop it — this is ego-dystonic.
OCD compulsions are typically ritualistic/rule-driven (must be done in a certain way, a certain number of times) and may be unrelated to the feared outcome they are intended to prevent and/or clearly excessive [7]. GAD checking behaviours are usually directly related to preventing the feared outcome and are not usually excessive or time-consuming [7].
Some obsessions may resemble delusions due to oddity of beliefs or compulsive behaviours and weak resistance [3]. The critical question is: "Do you recognise these thoughts as your own?"
- In OCD: "Yes, they're my thoughts, but they're horrible and I can't stop them" → ego-dystonic, own thoughts
- In schizophrenia with thought insertion: "No, someone is putting these thoughts in my head" → ego-alien, externally attributed
The Insight Spectrum — Watch Out!
OCD exists on an insight spectrum. With absent insight/delusional beliefs — the patient is completely convinced the OCD beliefs are true [1]. This can look virtually identical to a delusional disorder. The key is the content and history: OCD themes (contamination, checking, symmetry) are characteristic, and there is usually a longitudinal history of OCD symptoms that preceded the loss of insight. Also look for other psychotic features (hallucinations, thought disorder, negative symptoms) — if present, think schizophrenia.
In OCD, recurrent intrusive thoughts are present, but they are unrelated to a traumatic event. In PTSD, anxiety symptoms (worries, avoidance, arousal) are specifically related to traumatic events [9]. Both have intrusive thoughts and avoidance, but:
- PTSD intrusions = re-experiencing the trauma (flashbacks, nightmares of the event)
- OCD intrusions = unrelated to any specific event (contamination fears, checking doubts, etc.)
Note: Traumatic events can precipitate OCD onset, but the OCD content is typically about contamination, symmetry, etc. — not a replay of the trauma itself.
The OC-related disorders listed in both DSM-5 and ICD-11 share the compulsive quality but are distinguished by their restricted content domain [1][3]:
| Disorder | Content Domain | Obsessional Component? |
|---|---|---|
| Body Dysmorphic Disorder | Limited to concerns about physical appearance | Yes — preoccupation with perceived appearance defects |
| Trichotillomania | Limited to hair-pulling | No obsessions — driven by premonitory urge/tension |
| Hoarding Disorder | Exclusively difficulty discarding possessions | Variable — may have emotional attachment, not classic obsessions |
| Excoriation Disorder | Limited to skin-picking | No obsessions — driven by urge/tension |
| OCD | Multiple domains possible | Yes — intrusive, ego-dystonic obsessions |
OCD should be diagnosed when hoarding behaviour arises from obsessions typical of OCD (e.g., obsessions concerning incompleteness or harm — not discarding old newspapers because they may contain information that could prevent harm) [3]. If hoarding is ego-syntonic and not driven by typical OCD themes, diagnose Hoarding Disorder.
Both involve repetitive movements, but they differ fundamentally in purpose:
- Tics are typically less complex than compulsions and not aimed at neutralizing obsessions [3]
- Tics are preceded by premonitory sensory urges (a physical "itch" or tension in a body part)
- Compulsions are preceded by obsessions (a cognitive experience — an intrusive thought causing anxiety)
- Tic disorders may occur together with OCD [3] — up to 30% of OCD patients have tics, and this co-occurrence should be specified as tic-related OCD [1][5]
| Red Flag | Think Instead |
|---|---|
| Thoughts feel alien/inserted | Psychotic disorder |
| Temporal relationship to substance use | Substance-induced |
| Onset after age 40 with neurological signs | Organic cause (basal ganglia lesion, neurodegenerative disease) |
| Acute onset in a child after streptococcal infection | PANDAS |
| Intrusions specifically about a traumatic event | PTSD |
| Content exclusively about physical appearance | BDD |
| Content exclusively about food/weight/shape | Eating disorder |
| Ego-syntonic perfectionism without rituals | OCPD |
| Simple, brief, non-purposeful motor movements | Tic disorder |
| Worries about plausible real-life concerns | GAD |
| Mood-congruent ruminations with no compulsions | Depression |
High Yield Summary
- Always rule from the top of the diagnostic hierarchy downward: Organic → Substance → Psychotic → Mood → OCD → Personality
- The ego-dystonic test: OCD obsessions are ego-dystonic (senseless, unwanted); GAD worries are ego-syntonic; OCPD traits are ego-syntonic
- The ownership test: OCD thoughts are recognised as own; in psychosis with thought insertion, thoughts feel alien/externally imposed
- The content domain test: OCD has broad obsessional themes; BDD is limited to appearance; trichotillomania has no obsessions; hoarding is about difficulty discarding
- The trauma link test: PTSD intrusions are trauma-related; OCD intrusions are unrelated to specific trauma
- The purpose test: Compulsions aim to neutralise obsessions; tics are purposeless and preceded by sensory urges not cognitive obsessions
- Insight spectrum in OCD: Good/fair → poor → absent/delusional; absent insight OCD can mimic delusional disorder — look for characteristic OCD themes and absence of other psychotic features
- OCD and comorbidity: > 70% anxiety disorders, > 60% mood disorders, up to 30% tic disorders, 12% schizophrenia/schizoaffective — always screen for comorbidities
Active Recall - Differential Diagnosis of OCD
References
[1] Lecture slides: GC 171. Stress-related disorders and obsessive-compulsive disorder (Post-traumatic stress disorder adjustment disorder, acute stress disorder)_rev.pdf (p31, p35, p38) [3] Senior notes: ryanho-psych.md (Section 8.2 Obsessive-Compulsive Disorder — Differential Diagnoses, pp. 188–189) [5] Lecture slides: GC 171 (p38) — Co-morbidities of OCD [6] Senior notes: ryanho-psych.md (Hierarchy of diagnosis, p. 4) [7] Senior notes: ryanho-psych.md (Section 8.1 GAD — Differential Diagnoses, OCD vs GAD) [8] Senior notes: ryanho-psych.md (Body Dysmorphic Disorder, p. 206) [9] Senior notes: ryanho-psych.md (D/dx of PTSD — Anxiety and OCD) [10] Senior notes: ryanho-psych.md (Eating Disorders — Anxiety spectrum, OCD) [11] Senior notes: ryanho-psych.md (Somatic Symptom Disorder — D/dx OCD) [12] Lecture slides: GC 167. I feel very nervous Anxiety disorders.pdf (p27) — DDx for anxiety symptoms including physical disorder and substance abuse [13] Senior notes: ryanho-psych.md (D/dx of ASD — OCD)
Diagnostic Criteria, Diagnostic Algorithm, and Investigations for OCD
1. Diagnostic Criteria
OCD is a clinical diagnosis — there is no blood test, scan, or biomarker that confirms it. The diagnosis rests entirely on a careful psychiatric history and mental state examination, guided by standardised diagnostic criteria. Let's walk through both the DSM-5 and ICD-10 criteria in detail, explaining why each criterion exists.
This is presented across three lecture slides [1][2] and is the primary framework you should know:
| Criterion | DSM-5 Wording | Explanation — Why This Criterion Exists |
|---|---|---|
| A | Presence of obsessions, compulsions, or both | The core of the diagnosis. You need at least one of obsessions or compulsions — most patients (~90%) have both, but either alone is sufficient |
Obsessions are defined by both (1) and (2) [1][14]:
"(1) Recurrent and persistent thoughts, urges, or images that are experienced, at some time during the disturbance, as intrusive and unwanted, and that in most individuals cause marked anxiety or distress" [1][14]
"(2) The individual attempts to ignore or suppress such thoughts, urges, or images, or to neutralize them with some other thought or action (i.e. by performing a compulsion)" [1][14]
Why two sub-criteria? Criterion A1 establishes the nature of the obsessions (intrusive, unwanted, distressing). Criterion A2 establishes the response — the patient does not passively accept them but actively tries to suppress or neutralise them. This distinguishes obsessions from, say, pleasant daydreams or goal-directed planning.
Compulsions are defined by both (1) and (2) [1][15]:
"(1) Repetitive behaviours (e.g., hand washing, ordering, checking) or mental acts (e.g., praying, counting, repeating words silently) that the individual feels driven to perform in response to an obsession, or according to rules that must be applied rigidly" [1][15]
"(2) The behaviours or mental acts are aimed at preventing or reducing anxiety or distress, or preventing some dreaded event or situation; however, these behaviours or mental acts are not connected in a realistic way with what they are designed to neutralize or prevent, or are clearly excessive" [1][15]
Why two sub-criteria? Criterion B1 establishes the driven quality (compulsion = compelled to do). Criterion B2 is crucial — it captures the irrationality or excessiveness of the act. Washing your hands after using the toilet is rational; washing them 50 times until they bleed is "clearly excessive." Praying once before a meal is connected realistically to religious practice; praying 300 times to prevent your family from dying is "not connected in a realistic way."
Mental Acts Count as Compulsions!
A common exam mistake is to think compulsions must be observable behaviours. Mental acts (praying silently, counting in one's head, repeating words silently) are explicitly included in the DSM-5 definition [15]. Always ask about mental rituals — patients may not volunteer them because they assume "it's just in my head."
| Criterion | DSM-5 Wording | Explanation |
|---|---|---|
| B | "The obsessions or compulsions are time-consuming (take more than 1 hour/day), or cause clinically significant distress or impairment in social, occupational, or other important areas of functioning" [1][16] | This is the clinical significance threshold. Many people have mild OC traits; this criterion ensures we only diagnose OCD when it actually causes harm. The > 1 hour/day benchmark is a useful clinical rule of thumb (and is used in the Y-BOCS scoring system) |
| C | "Not attributable to the direct physiological effects of a substance or another medical condition" [16] | Rules out organic/substance-induced OC symptoms (e.g., stimulant-induced stereotypies, post-encephalitic OC symptoms, PANDAS) |
| D | "The disturbance is not better explained by the symptoms of another mental disorder" [16] | Rules out OC-like symptoms that are better accounted for by GAD (real-life worries), depression (mood-congruent ruminations), psychosis (delusions), BDD (appearance concerns), eating disorders (food/weight preoccupations), etc. |
| Specifier | Description |
|---|---|
| With good or fair insight | Recognises that OCD beliefs are definitely or most likely not true [1] |
| With poor insight | Thinks OCD beliefs are probably true [1] |
| With absent insight | Is completely convinced the OCD beliefs are true [1] |
| Tic-related | Current or past tic disorder [1] |
DSM-5 Does NOT Require Rejection of Beliefs
The DSM does not require patients to actually reject obsessional beliefs to make a diagnosis [3]. This is an important update from older criteria — even patients with absent insight/delusional conviction can be diagnosed with OCD, as long as the content and pattern fit OCD rather than a primary psychotic disorder.
The ICD-10 criteria are slightly different in emphasis [3]:
| Criterion | ICD-10 Wording | Key Differences from DSM-5 |
|---|---|---|
| Duration | Obsessional symptoms or compulsive acts must be present on most days for ≥ 2 successive weeks | ICD-10 specifies a minimum duration of 2 weeks; DSM-5 does not specify a minimum duration (relies on clinical significance instead) |
| (a) | They must be recognised as the individual's own thoughts or impulses | Explicitly requires ownership — this is implied in DSM-5 but stated explicitly in ICD-10 |
| (b) | There must be at least one thought or act that is still resisted unsuccessfully | Requires evidence of resistance — DSM-5 is softer on this, acknowledging resistance may wane over time |
| (c) | The thought of carrying out the act must not be in itself pleasurable (not including simple relief of tension or anxiety) | This distinguishes compulsions from impulsive acts (which are pleasurable, e.g., gambling, substance use). The relief experienced after a compulsion is not "pleasure" — it is tension reduction |
| (d) | The thoughts, images, or impulses must be unpleasantly repetitive | Emphasises the distressing, repetitive nature |
| Hierarchy note | If both depression and OC symptoms are present, precedence should be given to the symptoms that developed first, or if none predominates, regard depression as primary | ICD-10 applies the diagnostic hierarchy more strictly than DSM-5 |
| Subtypes | F42.0 predominantly obsessional thoughts or ruminations; F42.1 predominantly compulsive acts; F42.2 mixed obsessional thoughts and acts | ICD-10 offers subtyping by predominant presentation; DSM-5 uses insight and tic-related specifiers instead |
The ICD-11 (2019/2022) has updated the criteria. Key changes from ICD-10:
- OCD is moved from "Neurotic, stress-related and somatoform disorders" (F4) to a new category: "Obsessive-Compulsive and Related Disorders"
- The resistance requirement is relaxed (consistent with DSM-5)
- Insight specifiers are added (good/fair, poor, absent)
- Minimum duration requirement is retained but less rigid
Before a formal diagnostic assessment, screening can identify patients who may have OCD. The lecture slides provide a specific screening question [18]:
"Do you get thoughts stuck in your head that really bother you or need to do things over and over like washing your hands, checking things or count?" [18]
This single question captures both obsessions ("thoughts stuck in your head that really bother you") and compulsions ("need to do things over and over like washing, checking, counting"). It is elegant because it uses lay language and gives concrete examples that patients can relate to.
Other useful screening questions include:
- "Do you wash or clean a lot?"
- "Do you check things a lot?"
- "Is there any thought that keeps bothering you that you'd like to get rid of but can't?"
- "Do your daily activities take a long time to finish?"
- "Are you concerned about putting things in a special order, or are you very upset by mess?"
The following flowchart integrates the screening, assessment, diagnostic criteria, and specifier determination into a clinical decision pathway:
Step-by-Step Walkthrough
| Step | Action | Rationale |
|---|---|---|
| 1. Screen | Use screening question(s) above [18] | Efficient initial detection; OCD is frequently underdiagnosed because patients are embarrassed or do not recognise symptoms as a disorder |
| 2. Full History | Detailed psychiatric history: onset, course, content of obsessions/compulsions, triggers, avoidance, insight, family history, childhood symptoms, substance use, medical history | OCD is a clinical diagnosis — the history IS the investigation |
| 3. Mental State Examination | Appearance (dermatitis?), behaviour (rituals?), speech, mood (depressed? anxious?), thought form and content (obsessions? delusions?), perception, cognition, insight, risk | MSE provides objective data; insight assessment is critical for specifier determination |
| 4. Rule out organics | Medical history, substance history, neurological examination, consider blood tests if atypical | Organic mimickers (PANDAS, encephalitis lethargica, basal ganglia lesions) can present identically |
| 5. Apply diagnostic criteria | Criterion A → B → C → D sequentially | Systematic application ensures diagnostic rigour |
| 6. Specifiers | Assess insight level; screen for tics | Determines treatment approach (e.g., antipsychotic augmentation for absent insight or tic-related) |
| 7. Severity | Apply Y-BOCS | Quantifies severity; guides treatment intensity; monitors response |
| 8. Comorbidities | Screen for depression, anxiety, tics, substance use, suicide risk | > 60% have comorbid mood disorder; > 70% comorbid anxiety; suicide risk is elevated |
4. Investigation Modalities
OCD is fundamentally a clinical diagnosis. There are no diagnostic laboratory tests or imaging studies. However, investigations serve three purposes:
- Quantifying severity (to guide treatment and monitor progress)
- Ruling out organic causes (especially in atypical presentations)
- Screening for comorbidities
4.1 Severity Assessment Tools
The Y-BOCS is the gold standard for measuring OCD severity. Understanding it is high-yield.
Name breakdown: Yale-Brown → developed at Yale University and Brown University
Structure: 10 items, each scored 0–4, total score 0–40
| Item | Domain | What It Measures |
|---|---|---|
| Items 1–5 | Obsessions | Time occupied, interference, distress, resistance, control |
| Items 6–10 | Compulsions | Time occupied, interference, distress, resistance, control |
Severity thresholds:
| Y-BOCS Score | Severity | Clinical Implication |
|---|---|---|
| 0–7 | Subclinical | Monitoring; psychoeducation |
| 8–15 | Mild | Low-intensity CBT or watchful waiting |
| 16–23 | Moderate | SSRI or CBT (or both) |
| 24–31 | Severe | Combination SSRI + CBT; consider higher SSRI doses |
| 32–40 | Extreme | Intensive combined treatment; consider clomipramine or augmentation strategies |
Why the Y-BOCS is useful:
- It separates obsessions and compulsions — you can track each independently
- It measures five dimensions for each: time, interference, distress, resistance, and control — these capture different aspects of severity
- A ≥ 35% reduction in Y-BOCS score is typically considered a treatment response
- A score ≤ 12–14 is often used as the threshold for remission
| Scale | Purpose | Notes |
|---|---|---|
| Obsessive-Compulsive Inventory – Revised (OCI-R) | Self-report screening tool; 18 items | Useful for initial screening and monitoring; less clinician time required |
| Dimensional Obsessive-Compulsive Scale (DOCS) | Measures severity across 4 symptom dimensions (contamination, responsibility, unacceptable thoughts, symmetry) | Useful for profiling which dimension is dominant |
| Clinical Global Impression – Severity (CGI-S) | 1-item clinician-rated global severity | Quick, used in clinical trials alongside Y-BOCS |
| Children's Y-BOCS (CY-BOCS) | Modified Y-BOCS for paediatric use | For children and adolescents; similar structure |
These are not routine — they are indicated only when the clinical picture is atypical (e.g., acute onset, late onset after age 40, neurological signs, treatment resistance, presentation in a child post-infection):
| Investigation | When to Order | What You're Looking For | Key Findings/Interpretation |
|---|---|---|---|
| Basic bloods (FBC, RFT, LFT, TFT, glucose, calcium) | Atypical presentation; suspected medical cause; pre-treatment baseline | Thyroid dysfunction (can cause anxiety mimicking OCD); metabolic derangements; baseline before starting SSRIs | Abnormal TFTs → investigate thyroid disease; abnormal LFTs → caution with hepatically metabolised drugs |
| Anti-streptolysin O titre (ASOT) / Anti-DNAse B | Suspected PANDAS — acute onset OC symptoms in a child following sore throat/pharyngitis [3] | Evidence of recent streptococcal infection | Elevated ASOT ( > 200 IU/mL) or Anti-DNAse B → supports PANDAS diagnosis; temporal correlation with OC symptom onset is critical |
| Throat swab culture | Suspected PANDAS — to identify active Group A strep infection | Active streptococcal pharyngitis | Positive culture → treat infection; may lead to resolution of OC symptoms |
| Brain MRI | Atypical features: focal neurological signs, late onset, rapid progression, treatment resistance | Basal ganglia lesions (stroke, tumour, demyelination); caudate atrophy (Huntington's); frontal lobe lesions | Caudate/basal ganglia pathology → organic OC syndrome; frontal lobe pathology → consider frontotemporal dementia or tumour |
| EEG | Suspected temporal lobe epilepsy (episodic OC symptoms, altered consciousness, automatisms) | Temporal lobe epileptiform discharges | Temporal spikes → TLE as organic cause of OC-like symptoms |
| Autoimmune panel (anti-neuronal antibodies) | Suspected autoimmune encephalitis (acute onset, psychiatric + neurological symptoms) | Anti-NMDA receptor antibodies, anti-basal ganglia antibodies | Positive antibodies → autoimmune encephalitis; specific treatment (immunotherapy) may resolve OC symptoms |
| Urine drug screen | Suspected substance-induced OC symptoms | Stimulant use (amphetamines, cocaine) → can cause stereotyped behaviours resembling compulsions | Positive for stimulants → substance-induced; OC symptoms should resolve with cessation |
| Copper studies (ceruloplasmin, 24hr urine copper) | Young patient with movement disorder + psychiatric symptoms (suspect Wilson's disease) | Low ceruloplasmin, elevated urine copper | Wilson's disease affects basal ganglia → can cause OC symptoms among other psychiatric manifestations |
Before initiating pharmacotherapy (particularly SSRIs or clomipramine), the following baseline investigations may be warranted:
| Investigation | Reason |
|---|---|
| ECG | Particularly before starting clomipramine (tricyclic antidepressant) — check for prolonged QTc, conduction abnormalities. Also relevant for high-dose SSRIs (especially citalopram/escitalopram which can prolong QTc) |
| Baseline weight/BMI | SSRIs can cause weight changes; important for monitoring |
| LFTs | SSRIs and clomipramine are hepatically metabolised |
| U&Es/RFT | Baseline renal function; hyponatraemia risk with SSRIs (SIADH) |
| TFTs | Rule out thyroid dysfunction as comorbid/contributing factor |
| Pregnancy test | In women of childbearing age — SSRIs have category C/D risk; paroxetine specifically is category D (teratogenic, cardiac defects) |
These are mentioned in the notes for understanding pathophysiology, not for clinical diagnosis [3]:
| Modality | Findings in OCD | Clinical Relevance |
|---|---|---|
| Structural MRI | ↑ grey matter volume in striatum; ↓ in orbitofrontal, dorsomedial and anterior cingulate cortex [3] | Supports CSTC loop model; not used diagnostically |
| Functional MRI / PET | ↑ activity in orbitofrontal cortex, caudate, anterior cingulate, and thalamus [3] | Activity normalises with successful treatment (both SSRI and CBT); supports circuit-level model |
| Neurotransmitter studies | ↓ cortical 5-HT1A binding; inconsistent serotonin findings [3] | Explains why SSRIs help but does not confirm a simple serotonin deficit |
In clinical practice, the "investigation" for OCD IS the clinical interview. Here is how to structure it:
| Component | Key Areas to Cover | Why |
|---|---|---|
| History of presenting complaint | Onset (gradual vs acute), precipitants, course (continuous vs episodic), content of obsessions and compulsions (use the 4 dimensions: contamination, doubt/checking, symmetry, forbidden thoughts), time spent per day, degree of distress, impact on function, avoidance behaviours | Characterises the illness; determines severity; identifies themes for CBT |
| Insight assessment | "Do you think these thoughts/behaviours are reasonable?" "Do you believe X will really happen if you don't Y?" | Determines insight specifier; guides treatment (poor/absent insight → may need antipsychotic augmentation) |
| Resistance assessment | "Do you try to resist these thoughts/behaviours?" "What happens when you try?" | Part of diagnostic criteria (ICD-10); also indicates disease chronicity (resistance tends to diminish over time) |
| Comorbidity screen | Depression (PHQ-9), anxiety disorders (GAD-7), tics (ask about motor and vocal tics), substance use, eating patterns | > 60% have comorbid depression; > 70% comorbid anxiety; up to 30% comorbid tics [5] |
| Risk assessment | Suicidal ideation, self-harm, harm to others (particularly if aggressive obsessions are present — reassure that OCD patients almost never act on these) | Suicide risk is elevated in OCD, especially with comorbid depression |
| Family history | OCD, tic disorders, anxiety, depression in first-degree relatives | 4× risk in first-degree relatives; supports genetic contribution |
| Developmental history | Childhood onset, childhood adversity, PANDAS | 25% onset before age 14; PANDAS should be considered in paediatric acute onset |
| Premorbid personality | OCPD traits, other personality features | Prognostic implications; anankastic traits are over-represented |
| Collateral history | From family/carers — patients may minimise symptoms or have poor insight | Essential when insight is poor/absent; family may provide crucial behavioural observations |
High Yield Summary
- OCD is a clinical diagnosis — no blood test or scan confirms it. The clinical interview IS the investigation.
- DSM-5 Criterion A: Obsessions (intrusive, unwanted, cause distress + attempts to suppress/neutralise) and/or Compulsions (repetitive, driven, aimed at reducing distress but not realistically connected or clearly excessive)
- DSM-5 Criterion B: Time-consuming ( > 1 hour/day) OR clinically significant distress/impairment
- DSM-5 Criterion C: Not attributable to substance or medical condition
- DSM-5 Criterion D: Not better explained by another mental disorder
- Specifiers: Insight (good/fair, poor, absent/delusional) and Tic-related
- ICD-10 key differences: Requires ≥ 2 weeks duration; explicitly requires ownership of thoughts, resistance, and non-pleasurability; applies diagnostic hierarchy more strictly
- Y-BOCS is the gold standard severity scale (0–40; subclinical < 8, mild 8–15, moderate 16–23, severe 24–31, extreme 32–40)
- Screening question: "Do you get thoughts stuck in your head that really bother you, or need to do things over and over like washing your hands, checking things, or counting?"
- Organic workup is only needed in atypical presentations: ASOT for PANDAS, MRI for basal ganglia lesions, EEG for TLE, drug screen for substances
- Pre-treatment: ECG (especially before clomipramine or high-dose SSRI), LFTs, U&Es, TFTs, pregnancy test
Active Recall - OCD Diagnostic Criteria, Algorithm, and Investigations
References
[1] Lecture slides: GC 171. Stress-related disorders and obsessive-compulsive disorder (Post-traumatic stress disorder adjustment disorder, acute stress disorder)_rev.pdf (p33–35) [2] Lecture slides: GC 167. I feel very nervous Anxiety disorders.pdf (p31, p33–35) [3] Senior notes: ryanho-psych.md (Section 8.2 Obsessive-Compulsive Disorder — Diagnostic Criteria, pp. 187–189) [5] Lecture slides: GC 171 (p38) — Co-morbidities of OCD [14] Lecture slides: GC 167. I feel very nervous Anxiety disorders.pdf (p33) — DSM-5 OCD Criterion A, Obsessions [15] Lecture slides: GC 167. I feel very nervous Anxiety disorders.pdf (p34) — DSM-5 OCD Criterion A, Compulsions [16] Lecture slides: GC 167. I feel very nervous Anxiety disorders.pdf (p35) — DSM-5 OCD Criteria B-D [17] Lecture slides: GC 171 (p35) — OCD Specifiers [18] Lecture slides: GC 171 (p42) — Screening questions for psychiatric disorders
Management of OCD
Before diving into specific treatments, let's establish the key principles that govern OCD management:
Principle 1: OCD responds to a narrow range of treatments. Unlike depression where many classes of antidepressant work, OCD responds specifically to serotonergic agents (SSRIs, clomipramine) and CBT with ERP. Noradrenergic agents alone (e.g., desipramine, reboxetine) do not work for OCD. This specificity supports the serotonergic hypothesis of OCD pathophysiology.
Principle 2: OCD requires higher doses and longer duration. SSRIs for OCD typically require doses at the top of the therapeutic range and 8–12 weeks to show effect (vs. 4–6 weeks for depression). This suggests the mechanism in OCD is different from simple serotonin reuptake inhibition — it likely involves downstream receptor desensitisation and modulation of the CSTC loop.
Principle 3: Treatment response rates are moderate. 40–60% treatment response [19] — this means a substantial proportion of patients will need augmentation or combination strategies. Complete remission is even less common.
Principle 4: CBT and medication have comparable efficacy and complementary mechanisms. Cognitive behaviour therapy reduces resting state glucose metabolism or blood flow in the right caudate in treatment responders. Similar results have been obtained with drug treatment [20]. This is remarkable — both pharmacotherapy and psychotherapy normalise the same CSTC circuit hyperactivity, but through different entry points (bottom-up for drugs, top-down for CBT).
The approach is stepped care — start with the least intensive effective treatment and escalate if response is suboptimal [3]:
| Step | Intervention | When to Use |
|---|---|---|
| 1st line | SSRI or intensive CBT | Initial treatment for moderate-to-severe OCD [3] |
| 2nd line | Combination of SSRI + CBT | If response to single strategy is suboptimal [3] |
| 3rd line | Use clomipramine if SSRI fails | After adequate trial of ≥2 SSRIs [3] |
| 4th line | Add antipsychotic or combine clomipramine + citalopram | If response still suboptimal [3] |
3. Pharmacological Treatment
SSRIs are first-line for OCD because they have the best side-effect profile [3][21].
How SSRIs work in OCD: SSRIs block the serotonin transporter (SERT) → ↑ synaptic 5-HT availability → over weeks, this leads to desensitisation of presynaptic 5-HT1A autoreceptors and postsynaptic 5-HT receptor changes → modulation of serotonergic tone in the CSTC loop → ↓ hyperactivity of the OFC-caudate-thalamic circuit → ↓ obsessions and compulsions.
Why higher doses are needed in OCD vs depression: The SERT occupancy required to modulate the CSTC loop in OCD appears to be higher than that needed for the mood circuits in depression. Studies suggest that OCD requires ~80% SERT occupancy (achieved at higher doses) vs ~60–70% for depression.
| SSRI | Starting Dose | Target OCD Dose | Notes |
|---|---|---|---|
| Fluoxetine | 20 mg/day | 40–80 mg/day | Long half-life (advantage: missed doses matter less; disadvantage: slow washout if switching) |
| Fluvoxamine | 50 mg/day | 200–300 mg/day | Particularly well-studied in OCD; licensed for OCD in many countries; significant CYP1A2 inhibition |
| Sertraline | 50 mg/day | 150–200 mg/day | Good evidence base; relatively few drug interactions |
| Paroxetine | 20 mg/day | 40–60 mg/day | Potent; but highest risk of discontinuation syndrome among SSRIs due to short half-life and anticholinergic properties; category D in pregnancy (cardiac defects) |
| Citalopram | 20 mg/day | 40 mg/day (max; QTc risk above this) | Clean pharmacology; but QTc prolongation limits dose escalation |
| Escitalopram | 10 mg/day | 20–30 mg/day | S-enantiomer of citalopram; slightly better tolerability; also QTc risk at high doses |
Key prescribing principles for SSRIs in OCD:
- Duration: ≥ 1–2 years after achieving remission, then slowly tapered [3]
- Relapse is common in the first few weeks after stopping [3]
- Start low, go slow — but titrate to the maximum tolerated dose before declaring treatment failure
- Allow 8–12 weeks at adequate dose before assessing response (vs 4–6 weeks for depression)
- An adequate trial = maximum tolerated dose for ≥ 8–12 weeks
- Try at least 2 different SSRIs before moving to clomipramine
Common side effects of SSRIs (explained mechanistically):
| Side Effect | Mechanism | Clinical Relevance |
|---|---|---|
| GI upset (nausea, diarrhoea) | ↑ 5-HT stimulates 5-HT3 receptors in GI tract | Usually transient (1–2 weeks); advise taking with food |
| Sexual dysfunction | ↑ 5-HT inhibits dopaminergic and noradrenergic pathways involved in sexual arousal/orgasm | Common (~30–50%); major cause of non-adherence; consider switching to agent with less sexual SE |
| Initial anxiety/agitation | Acute ↑ 5-HT stimulates 5-HT2C receptors → anxiogenic | Particularly relevant in OCD — warn patients symptoms may temporarily worsen; consider short-term benzodiazepine cover |
| Weight gain | Complex — 5-HT2C receptor effects on appetite regulation | More with paroxetine; less with fluoxetine |
| Hyponatraemia (SIADH) | ↑ 5-HT stimulates ADH release | Particularly in elderly; monitor Na+ if symptomatic |
| QTc prolongation | Direct cardiac ion channel effects | Particularly citalopram/escitalopram at high doses; obtain baseline ECG |
| Discontinuation syndrome | Abrupt cessation → rapid ↓ in synaptic 5-HT; receptor upregulation not yet reversed | Worst with paroxetine (short half-life); always taper slowly |
OCD ≠ Depression Dosing
A very common exam and clinical mistake is to treat OCD with "depression doses" of SSRIs. If a patient with OCD is on fluoxetine 20 mg and not responding, the answer is NOT "treatment failure" — it's "dose is too low." You must titrate to the maximum tolerated dose (e.g., fluoxetine 80 mg) and wait 8–12 weeks before declaring non-response.
Clomipramine is a tricyclic antidepressant (TCA) that is the most potent serotonin reuptake inhibitor among TCAs. Its name: "chloro" + "imipramine" — it is a chlorinated derivative of imipramine.
Clomipramine is used if SSRI fails [3][21].
Why clomipramine works for OCD: Clomipramine is an extremely potent SERT blocker (more potent than most SSRIs). Its active metabolite, desmethylclomipramine, also inhibits noradrenaline reuptake, but the parent compound's serotonergic action is what drives the anti-obsessional effect.
Why it's not first-line: The side-effect profile is significantly worse than SSRIs:
| Side Effect | Mechanism |
|---|---|
| Anticholinergic effects (dry mouth, constipation, urinary retention, blurred vision) | Muscarinic receptor blockade |
| Sedation | Histamine H1 receptor blockade |
| Orthostatic hypotension | Alpha-1 adrenergic blockade |
| Weight gain | H1 and 5-HT2C effects |
| QTc prolongation / cardiac arrhythmia | Sodium channel blockade in cardiac myocytes |
| Seizure risk | Lowered seizure threshold at high doses |
| Lethal in overdose | Sodium channel blockade → cardiac conduction block → VF/asystole |
Prescribing: Start 25 mg/day, titrate to 100–250 mg/day. ECG mandatory before starting and at dose increases (check QTc). Contraindicated in recent MI, heart block, severe liver disease.
Venlafaxine is listed as an alternative to SSRIs [3]. It is an SNRI ("serotonin-noradrenaline reuptake inhibitor") — at lower doses it acts predominantly as an SRI, and at higher doses it recruits noradrenergic blockade. The anti-OCD effect is likely mediated primarily by the serotonergic component.
Evidence for venlafaxine in OCD is weaker than for SSRIs or clomipramine — it is used when SSRIs and clomipramine cannot be used or have failed.
3.4 Augmentation Strategies
When monotherapy is insufficient, augmentation is the next step:
Antipsychotics (haloperidol, risperidone, quetiapine, olanzapine, aripiprazole) are used as augmentation [3].
Why antipsychotics help in OCD: The CSTC loop involves dopaminergic modulation at the striatal level. Adding a dopamine blocker may help "brake" the hyperactive loop. This is particularly effective in:
- Tic-related OCD (shared striatal dopaminergic pathology with tic disorders)
- OCD with poor/absent insight (delusional-like conviction may have a dopaminergic component)
- OCD with comorbid tics or Tourette's
| Antipsychotic | Evidence Level | Notes |
|---|---|---|
| Risperidone (0.5–3 mg/day) | Best evidence | Multiple RCTs; NNT ~4–5 |
| Aripiprazole (5–15 mg/day) | Good evidence | Partial D2 agonist — may be better tolerated; less metabolic SE |
| Haloperidol (2–5 mg/day) | Moderate evidence | Particularly for tic-related OCD; EPS risk |
| Quetiapine (150–450 mg/day) | Mixed evidence | Sedation may be useful if insomnia is prominent |
| Olanzapine (5–10 mg/day) | Some evidence | Significant metabolic side effects (weight gain, diabetes) |
Duration of augmentation trial: 4–6 weeks at adequate dose before assessing response.
Combining clomipramine + citalopram is listed as a 4th-line option [3]. This is pharmacologically rational (two serotonergic agents via different mechanisms) but requires specialist supervision due to:
- Risk of serotonin syndrome (↑↑ synaptic 5-HT → hyperthermia, rigidity, clonus, autonomic instability)
- Combined QTc prolongation risk
- Requires ECG monitoring and careful dose titration
| Agent | Mechanism | Evidence |
|---|---|---|
| Lithium | Enhances serotonergic transmission | Weak evidence for OCD (unlike its strong evidence in depression augmentation) |
| N-acetylcysteine (NAC) | Glutamate modulator (restores glutamate homeostasis in striatum) | Emerging evidence; low risk; sometimes used as adjunct |
| Memantine | NMDA receptor antagonist → glutamate modulation | Small studies show benefit; targets glutamatergic CSTC dysfunction |
| Riluzole | Glutamate release inhibitor | Used in ALS; small OCD studies show promise |
| D-cycloserine | Partial NMDA agonist → facilitates extinction learning | Used to augment CBT/ERP (given before ERP sessions to enhance fear extinction) |
Anxiolytics are used for short-term relief, but not more than 2–4 weeks at a time [3].
Why short-term only? Benzodiazepines (BZDs) enhance GABA-A receptor function → rapid anxiolysis. However:
- They do NOT treat the core OCD pathology (CSTC loop hyperactivity)
- Tolerance and dependence develop rapidly (within 2–4 weeks)
- Withdrawal can exacerbate anxiety
- They impair the learning that occurs during CBT/ERP (BZDs dampen the anxiety that is therapeutically necessary for habituation)
Role: Bridge therapy during the initial 2–4 weeks of SSRI treatment when anxiety may paradoxically worsen due to acute serotonergic stimulation.
4. Non-Pharmacological Treatment
Psychoeducation to improve patient's understanding and reassurance [3][22].
This is always the first step. Key points to communicate:
- OCD is a recognised medical condition, not a character flaw
- The intrusive thoughts do NOT mean the patient will act on them (crucial for those with aggressive/sexual obsessions)
- Treatment is effective in the majority of cases
- Both medication and psychological therapy work
- Recovery takes time — 8–12 weeks for medication, typically 12–16 sessions for CBT
Psychological support and reassurance [22] — but note that excessive reassurance-seeking from the therapist can itself become a compulsion. The therapist must balance being supportive while not feeding into the OCD cycle.
This is the gold-standard psychological treatment for OCD.
Name breakdown:
- Exposure = deliberate confrontation with the feared stimulus/obsessional trigger
- Response Prevention = deliberately NOT performing the compulsion
Exposure and response prevention (ERP) involves exposure to environmental cues that increase symptoms, but preventing the compulsive response (e.g., stopping the patient from washing their hands when they want to) [3].
Why ERP works — from first principles:
- The obsession triggers anxiety → the compulsion provides temporary relief (negative reinforcement)
- This relief prevents the natural process of habituation (the brain's ability to learn that the feared outcome does not occur)
- By blocking the compulsion (response prevention) while maintaining exposure to the trigger:
- Anxiety initially spikes (this is expected and patients must be warned)
- Over time (typically 45–90 minutes), anxiety naturally decreases through habituation
- With repeated sessions, the brain learns: "I touched the 'contaminated' surface, I didn't wash, and nothing bad happened"
- This weakens the obsession-anxiety-compulsion cycle
Effect: ~2/3 with moderately severe rituals improve substantially, comparable to SSRIs [3].
Limitations: Less effective for obsessional thoughts that occur without rituals [3] — because pure obsessions have no overt compulsion to prevent. For these patients, the cognitive component is more important.
Typical protocol: 12–16 sessions, each 60–90 minutes, with between-session homework (self-directed ERP). A hierarchy of feared situations is constructed from least to most anxiety-provoking, and exposure progresses gradually.
Cognitive therapy as part of CBT [3]:
Involves: tackling underlying cognitive beliefs of obsessive thoughts [3]:
-
Thought stopping and distraction for ruminations [3][22] — resistive thoughts only increase their occurrence [22]. This is a counterintuitive but crucial principle: the more you try to suppress a thought, the more it rebounds (Wegner's "white bear" experiment). Instead, patients learn to acknowledge the thought without engaging with it.
-
Modification of responsibility beliefs: Try to suggest less threatening alternative explanations and discuss any other cognitive distortions [3]. For example:
- "Having the thought 'I might harm my child' does NOT mean I am a dangerous person" (thought-action fusion)
- "Just because I thought about contamination does NOT mean I am contaminated" (magical thinking)
- "I am not personally responsible for preventing every possible harm" (inflated responsibility)
Effect: not as effective on its own but increases the effect of behavioural interventions when combined [3].
Why CBT Works at the Brain Level
Increased activity in the right caudate is found in patients with OCD, and cognitive behaviour therapy reduces resting state glucose metabolism or blood flow in the right caudate in treatment responders. Similar results have been obtained with drug treatment [20]. This means CBT and SSRIs converge on the same neural target — the hyperactive caudate in the CSTC loop — through different pathways. CBT works "top-down" (cortical cognitive reappraisal → ↓ OFC drive → ↓ caudate activity), while SSRIs work "bottom-up" (↑ serotonin → modulate striatal gating → ↓ loop hyperactivity).
4.5 Neurosurgical Interventions (Last Resort)
For treatment-refractory OCD (failed multiple adequate pharmacological trials + CBT):
Psychosurgery: orbitomedial/cingulate lesioning → dramatic decrease in tension and stress in severe cases [3].
- Anterior capsulotomy: lesions the anterior limb of the internal capsule (disrupts the connection between OFC and thalamus in the CSTC loop)
- Cingulotomy: lesions the anterior cingulate cortex (disrupts the error-monitoring component)
- These are irreversible and reserved for the most severe, treatment-refractory cases
- Response rates ~30–50% in carefully selected patients
- Risks: personality change, apathy, seizures, cognitive impairment
Deep brain stimulation (DBS): increasingly used for intractable OCD but experience is still limited [3].
- Targets: ventral capsule/ventral striatum, subthalamic nucleus, nucleus accumbens
- Mechanism: high-frequency electrical stimulation → functional inhibition of the target → disrupts the hyperactive CSTC loop
- Advantage over psychosurgery: reversible and adjustable
- Disadvantage: requires permanent implanted hardware; risk of infection, lead migration, battery replacement
- FDA-approved under a Humanitarian Device Exemption for severe, treatment-refractory OCD
- Response rates ~60% in carefully selected patients
The lecture slides emphasize the following broader treatment framework [19][21][23]:
General treatment approaches [23]:
- Pharmacotherapy: Antidepressants, Anxiolytics, Antipsychotics, Mood stabilizers
- Psychotherapy: Cognitive Behaviour Therapy (CBT), Mindfulness-based Therapy
Treatment of Anxiety Disorders (which includes OCD in the lecture context) [21]:
- Supportive measures: Explanation, Reassurance
- Psychological treatment: Cognitive behavioural therapy
- Medications: Antidepressants (e.g., SSRI, SNRI, TCA, MAOI), Beta-adrenergic antagonist (e.g., propranolol), Benzodiazepines, Buspirone, Pregabalin
For OCD specifically from the antidepressant slide [21]:
- SSRI: Paroxetine, Citalopram, Escitalopram, Fluoxetine, Sertraline, Fluvoxamine
- TCA: Clomipramine: OCD (specifically highlighted for OCD)
Key Lecture Summary Point
There are many effective treatments including psychotherapy and psychopharmacology. There is a huge amount of suffering associated with these disorders [24]. The lecture specifically reminds us that despite effective treatments being available, OCD causes enormous suffering — partly because it is underdiagnosed, undertreated, and patients often wait 7–10 years before seeking help due to shame and stigma.
| Population | Considerations |
|---|---|
| Children and adolescents | CBT with ERP is first-line; SSRIs (fluoxetine, fluvoxamine, sertraline have best evidence) as second-line; lower starting doses; screen for PANDAS in acute onset; involve family in treatment |
| Pregnancy | CBT is first-line (no drug exposure risk). If medication needed: sertraline and fluoxetine have most safety data. Avoid paroxetine (teratogenic — cardiac defects). Clomipramine should generally be avoided. Risk-benefit discussion essential |
| Elderly | Start SSRIs at lower doses; heightened risk of hyponatraemia (SIADH), falls, drug interactions; cognitive side effects of clomipramine particularly problematic |
| Tic-related OCD | May benefit from earlier antipsychotic augmentation (especially haloperidol or aripiprazole) given shared striatal dopaminergic pathology |
| OCD with absent insight | May need antipsychotic augmentation earlier; CBT may be less effective without insight; motivational approaches may help |
| Comorbid depression | Treat OCD first (SSRIs treat both); if depression is severe and independent, may need specific depression management (e.g., higher SSRI dose, augmentation with lithium/antipsychotic, or ECT for depression) |
| Timepoint | Action |
|---|---|
| Baseline | Y-BOCS score, comorbidity screen, risk assessment, ECG if using clomipramine/high-dose SSRI, bloods (LFT, RFT, TFT) |
| 2–4 weeks | Review tolerability of medication; assess for initial worsening of anxiety; suicide risk check |
| 8–12 weeks | First assessment of treatment response (Y-BOCS); if inadequate response at adequate dose → escalate |
| 6 months | Continue effective treatment; ongoing CBT reinforcement; assess functional improvement |
| 1–2 years | If in sustained remission, consider slow taper of medication (over 6–12 months); continue CBT skills as relapse prevention |
| Relapse | Return to previously effective dose; consider long-term/indefinite treatment if ≥ 2 relapses |
| Treatment | Indications | Contraindications / Cautions |
|---|---|---|
| SSRIs | First-line for all OCD; moderate-severe; all age groups | Caution: QTc prolongation (citalopram/escitalopram at high doses); pregnancy (avoid paroxetine); serotonin syndrome risk with MAOIs (absolute contraindication to combine); bleeding risk with NSAIDs/anticoagulants |
| Clomipramine | SSRI failure (≥ 2 adequate trials); severe OCD | Contraindicated: recent MI, heart block, severe liver disease, concurrent MAOI, epilepsy (relative). Caution: elderly (anticholinergic), suicidal patients (lethal in overdose) |
| Venlafaxine | Alternative when SSRIs and clomipramine not tolerated | Caution: hypertension (monitor BP at doses > 150 mg); discontinuation syndrome; serotonin syndrome risk |
| Antipsychotic augmentation | Partial/non-response to SSRI ± CBT; tic-related OCD; poor insight OCD | Caution: metabolic syndrome (olanzapine, quetiapine); EPS/tardive dyskinesia (haloperidol); prolactinaemia (risperidone) |
| CBT with ERP | First-line (equivalent to SSRIs); all severities; preferred in pregnancy/children; obsessional ruminations respond better to cognitive component | Relative contraindications: severe depression (may impair engagement); active psychosis; substance intoxication; patient refusal; severe intellectual disability |
| Benzodiazepines | Short-term anxiolysis (≤ 2–4 weeks) while waiting for SSRI to take effect | Contraindicated for long-term use; avoid in patients with substance use history; impairs CBT learning |
| DBS | Severe, treatment-refractory OCD (failed ≥ 3 adequate medication trials + CBT) | Requires neurosurgical centre of expertise; medical contraindications to neurosurgery |
| Psychosurgery | Absolute last resort; severe, treatment-refractory OCD | Irreversible; significant risk of personality change; requires multidisciplinary review and ethical approval |
High Yield Summary
- Stepped care: 1st line = SSRI or intensive CBT → 2nd line = SSRI + CBT → 3rd line = clomipramine → 4th line = add antipsychotic or clomipramine + citalopram
- SSRIs: First-line pharmacotherapy; require higher doses than depression (max tolerated dose); 8–12 weeks to assess response; continue ≥ 1–2 years after remission then slow taper
- Clomipramine: Most potent SRI; reserved for SSRI failure; significant side effects (anticholinergic, cardiac, lethal in overdose); ECG mandatory
- Antipsychotic augmentation: For partial/non-responders; risperidone and aripiprazole have best evidence; especially useful in tic-related and poor-insight OCD
- CBT with ERP: Gold-standard psychotherapy; ~2/3 improve; works by blocking compulsion → allowing habituation → breaking obsession-anxiety-compulsion cycle; less effective for pure obsessions without rituals
- Cognitive therapy: Targets inflated responsibility, thought-action fusion, magical thinking; enhances ERP effect when combined
- Both CBT and SSRIs normalise CSTC loop hyperactivity — CBT reduces right caudate hyperactivity in treatment responders
- Anxiolytics: Short-term only (≤ 2–4 weeks); bridge therapy; do NOT treat core pathology; impair CBT learning
- Neurosurgery: DBS (reversible, ~60% response) or psychosurgery (irreversible, ~30–50% response) for treatment-refractory cases only
- Treatment response rate: 40–60% overall; complete remission less common → importance of combination and augmentation strategies
- Key side-effect vigilance: QTc (clomipramine, high-dose SSRI), serotonin syndrome (SSRI + clomipramine), initial anxiety worsening with SSRI initiation
Active Recall - OCD Management
References
[2] Lecture slides: GC 167. I feel very nervous Anxiety disorders.pdf (p31, p36–37, p40) [3] Senior notes: ryanho-psych.md (Section 8.2 Obsessive-Compulsive Disorder — Management, pp. 189–190) [19] Lecture slides: GC 171. Stress-related disorders and obsessive-compulsive disorder (Post-traumatic stress disorder adjustment disorder, acute stress disorder)_rev.pdf (p41) — Treatment [20] Lecture slides: GC 171 (p40) — Functional imaging studies [21] Lecture slides: GC 167. I feel very nervous Anxiety disorders.pdf (p36–37) — Treatment of Anxiety Disorders; Antidepressants [22] Lecture slides: GC 167. I feel very nervous Anxiety disorders.pdf (p40) — Psychotherapy for OCD [23] Lecture slides: GC 171 (p17) — General treatment approaches [24] Lecture slides: GC 171 (p43) — Summary
Complications of OCD
OCD is not a benign condition. Left untreated — and even when treated — it can produce a cascading set of complications that touch every domain of a patient's life: psychiatric, physical, social, occupational, and existential. The lecture slides explicitly remind us: there is a huge amount of suffering associated with these disorders [24]. Let's work through the complications systematically, explaining the "why" behind each.
1. Psychiatric Complications
These are the most common and most clinically important complications. They arise because chronic, distressing, ego-dystonic obsessions and the exhausting cycle of compulsions erode mental health across multiple dimensions.
| Feature | Detail |
|---|---|
| Prevalence | > 60% lifetime diagnosis of a mood disorder, MDD being the most common (~41%) [5] |
| Relationship | Can be secondary to OCD (reactive/demoralisation depression) or a primary comorbidity (shared serotonergic pathology) |
Why does OCD cause depression? From first principles:
- Chronic distress: The patient endures hours daily of intrusive, ego-dystonic thoughts they cannot control → learned helplessness → demoralisation
- Functional impairment: OCD progressively restricts the patient's life — they cannot work, socialise, or engage in pleasurable activities → behavioural withdrawal → depressive symptoms
- Self-criticism and shame: Because the obsessions are ego-dystonic ("I know this is irrational but I can't stop"), patients often feel defective, weak, or "crazy" → ↓ self-esteem → depressive cognitions
- Shared neurobiology: Both OCD and depression involve serotonergic dysfunction, and the CSTC loop connects to limbic circuits involved in mood regulation
- Bidirectional relationship: Depression worsens OCD (depressive cognitions amplify the catastrophic appraisals underlying obsessions), and OCD worsens depression (more OC symptoms → more demoralisation)
Clinical significance: Comorbid depression is a worse prognostic factor [3] — it reduces engagement with CBT (apathy, hopelessness impair the effort required for ERP), increases suicide risk, and predicts poorer treatment response.
| Feature | Detail |
|---|---|
| Lifetime suicidal ideation | ~63% of OCD patients |
| Lifetime suicide attempts | ~26% of OCD patients |
| Completed suicide | Elevated risk compared to general population, though lower than in depression or schizophrenia alone |
Why is suicide risk elevated?
- Chronic suffering without relief: OCD rarely remits (~20% in 40 years) if untreated [3] — years of unrelenting distress erodes the will to continue
- Comorbid depression: The single strongest predictor of suicidality in OCD
- Hopelessness: Especially in treatment-refractory OCD, patients may feel there is "no way out"
- Shame and secrecy: Many patients conceal their symptoms for years due to shame (especially those with taboo obsessions about sexuality, violence, or religion) → social isolation → suicide risk
- Absent insight: Patients with delusional-level conviction may experience greater distress because they genuinely believe the catastrophic consequences of their obsessions
Suicide Risk Assessment in OCD
Do NOT assume that OCD patients are at low suicide risk simply because "it's an anxiety disorder." Always actively assess suicidal ideation, particularly in patients with comorbid depression, poor insight, treatment resistance, and social isolation. Patients with aggressive/violent obsessions may be at particular risk of shame-driven suicidality — but importantly, these patients almost NEVER act on their violent obsessions (the ego-dystonic nature means the obsession is the opposite of what the patient wants).
> 70% have a lifetime diagnosis of an anxiety disorder such as panic disorder, social anxiety disorder, GAD, and phobia [5].
Why the high comorbidity?
- Shared anxiety circuitry: The amygdala-prefrontal circuits involved in anxiety disorders overlap with the CSTC loop involved in OCD
- Shared genetic vulnerability: Common genetic variants (affecting serotonin, GABA, and glutamate systems) predispose to both OCD and other anxiety disorders
- Behavioural overlap: The avoidance behaviour in OCD can generalise to produce phobia-like presentations; the hypervigilance can resemble GAD
Specific patterns:
- Social anxiety disorder: Avoidance of public situations due to contamination fears or fear of performing rituals in public → mimics and may co-occur with SAD
- Panic disorder: Intense anxiety from obsessions can escalate to panic attacks → some OCD patients develop comorbid panic disorder
- Specific phobias: Obsessional phobias (e.g., avoiding kitchens due to knife-related obsessions) may evolve into specific phobia-like presentations
Up to 30% have a lifetime tic disorder [5].
This is not merely comorbidity — there is shared striatal pathology. Tic-related OCD has distinct features:
- Earlier age of onset
- Male predominance
- More symmetry/ordering obsessions
- More "just right" feelings (sensory rather than cognitive)
- Poorer response to SSRIs alone → often requires antipsychotic augmentation
| Feature | Detail |
|---|---|
| Prevalence | ~25–30% lifetime |
| Common substances | Alcohol, benzodiazepines (self-medication for anxiety), cannabis |
Why? Patients use substances to self-medicate the chronic anxiety and distress of OCD. Alcohol and benzodiazepines are GABAergic → rapidly reduce anxiety → powerful negative reinforcement → dependence risk. This is particularly insidious because the substance provides temporary relief but worsens OCD in the long run (disrupts sleep architecture, impairs cognitive processing, interferes with CBT).
| Feature | Detail |
|---|---|
| Prevalence | OCD comorbidity in AN/BN: ~15–35% |
| Overlap | Ritualistic eating behaviours, symmetry/ordering of food, contamination fears about food |
The shared compulsive quality links OCD and eating disorders. Both involve repetitive, rule-governed behaviours driven by anxiety. Anorexia nervosa in particular shares the rigidity and perfectionism associated with the OFC-striatal circuit.
| Comorbidity | Prevalence | Notes |
|---|---|---|
| Schizophrenia/schizoaffective | 12% [5] | OC symptoms are common in schizophrenia; shared caudate pathology; antipsychotics (especially clozapine) can paradoxically worsen OC symptoms via 5-HT2A antagonism |
| Bipolar disorder | ~10–15% | Mania can disinhibit compulsions; depression phase worsens OCD |
| OCPD | 23–32% [3] | Over-represented but distinct from OCD; anankastic traits may predispose to OCD onset |
| Body Dysmorphic Disorder | ~12–15% | Shared OC-spectrum pathology; overlapping CSTC dysfunction |
2. Functional and Social Complications
These are the "silent" complications — they don't appear on blood tests but devastate quality of life.
Why? OCD consumes enormous time (the obsessions or compulsions take > 1 hour/day [1] — and in severe cases, 6–8+ hours/day). This directly reduces productive work time. Additionally:
- Checking rituals delay task completion
- Contamination avoidance restricts which workplaces/tasks are tolerable
- Concentration is impaired by constant intrusive thoughts
- Sick days accumulate due to depression and exhaustion
Studies show OCD patients have significantly higher rates of unemployment, underemployment, and occupational disability compared to matched controls. The economic burden is substantial.
Why? Avoidance behaviour may become pervasive and severely restrict functioning [3]:
- Contamination fears → avoidance of public spaces, social gatherings, physical contact → social isolation
- Shame about symptoms → concealment → emotional distance from friends and family
- Reassurance-seeking → strains relationships (partners/family become frustrated with constant demands for reassurance)
- Family accommodation → family members adapt their own behaviour to accommodate the patient's OCD (e.g., washing their own hands repeatedly, avoiding certain words/topics) → reinforces OCD and creates dysfunctional family dynamics
Particularly relevant given that 25% of OCD onset is before age 14 [3]. Children and adolescents with OCD may:
- Spend hours on homework due to checking/perfectionism → poor academic performance despite normal intelligence
- Avoid school due to contamination or social fears
- Be misidentified as having ADHD (poor concentration) or behavioural problems
- Marital/partner relationships: OCD is associated with higher rates of relationship dissatisfaction, separation, and divorce. Partners experience caregiver burden, frustration, and their own psychological distress
- Parent-child relationships: Parents with OCD may impose rituals on their children (e.g., excessive cleaning rules); children may learn maladaptive anxiety responses (modelling)
- Family accommodation: When family members participate in rituals or modify their behaviour to reduce the patient's distress, this paradoxically reinforces the OCD cycle
These arise directly from the compulsive behaviours themselves.
| Complication | Mechanism | Example |
|---|---|---|
| Contact dermatitis / eczematous changes | Excessive handwashing → disruption of skin lipid barrier → irritant contact dermatitis → cracking, bleeding, secondary infection | Patient washes hands 50+ times/day with harsh soap; hands are raw, erythematous, fissured |
| Chemical burns | Use of harsh disinfectants (bleach, alcohol) on skin | Patient uses undiluted bleach to "decontaminate" hands |
| Trichotillomania-related | Compulsive hair pulling → focal alopecia, folliculitis, scarring alopecia | Traction and mechanical damage to hair follicles |
| Excoriation | Compulsive skin picking → ulceration, scarring, secondary infection | Open wounds, especially on face, arms, legs |
| Musculoskeletal strain | Repetitive motor rituals (e.g., tapping, touching, rearranging) → overuse injuries | Tendinitis, carpal tunnel syndrome from repetitive actions |
| Obsessional slowness → nutritional deficiency | Eating rituals so elaborate that inadequate nutrition is consumed → malnutrition, weight loss | Patient takes 3 hours per meal due to counting/arrangement rituals; gives up eating altogether |
| Dental erosion | If OCD manifests as excessive tooth brushing | Enamel erosion, gum recession |
| Iatrogenic — medication side effects | SSRIs: GI upset, sexual dysfunction, weight gain, hyponatraemia, QTc prolongation. Clomipramine: anticholinergic effects, cardiac conduction abnormalities, seizures. Antipsychotics: metabolic syndrome, EPS, tardive dyskinesia | Complication of treatment, not the disease itself — but very real and a major cause of non-adherence |
4. Complications Related to Treatment Resistance and Chronicity
- Defined as failure to respond to ≥ 2 adequate SSRI trials + adequate CBT with ERP
- Affects ~30–40% of patients
- Leads to escalation to clomipramine, augmentation strategies, and ultimately consideration of neurosurgical interventions (DBS, psychosurgery)
- The longer OCD goes untreated, the more entrenched the CSTC loop hyperactivity becomes — akin to a "neuroplastic groove" that becomes harder to reverse
OCD rarely remits (~20% in 40 years) if untreated [3]. Even with treatment:
Over time, some patients' insight may deteriorate from good/fair → poor → absent/delusional. With absent insight, the patient is completely convinced the OCD beliefs are true [1]. This creates a clinical crisis:
- CBT becomes less effective (patient does not see the obsessions as irrational)
- The presentation begins to resemble a psychotic disorder → risk of misdiagnosis and inappropriate treatment
- Social functioning deteriorates further (patient acts on delusional beliefs)
- May require antipsychotic augmentation
| Population | Specific Complications |
|---|---|
| Perinatal OCD | Postpartum periods can lead to new onset or exacerbation of OCD [3]. Maternal OCD with harm-related obsessions (e.g., intrusive images of harming the baby) causes extreme distress and may interfere with bonding and caregiving. Risk of being misidentified as a risk to the child (these patients are horrified by their thoughts and do NOT act on them — distinguishing them from true postpartum psychosis is critical) |
| Paediatric OCD | Academic failure, social developmental arrest, family disruption, risk of PANDAS. Children may not report obsessions (lack of metacognitive ability to describe intrusive thoughts as "own but unwanted") → diagnosis may be delayed |
| OCD in schizophrenia | Clozapine (gold standard for treatment-resistant schizophrenia) can worsen or induce OC symptoms via 5-HT2A antagonism → creates a therapeutic dilemma. 12% of schizophrenia/schizoaffective patients have OCD [5] |
| Elderly | ↑ risk of medication side effects (hyponatraemia from SSRIs, anticholinergic toxicity from clomipramine, metabolic effects from antipsychotics); cognitive decline may impair CBT engagement; OCD may be misattributed to early dementia |
High Yield Summary
- Depression is the single most common complication: > 60% lifetime mood disorder (MDD most common); arises from chronic distress, functional impairment, and shared serotonergic pathology; worsens prognosis
- Suicidality is significantly elevated: ~63% lifetime ideation, ~26% attempts; driven by comorbid depression, hopelessness, shame, treatment resistance, and absent insight
- Anxiety disorder comorbidity: > 70% lifetime; shared circuitry and genetic vulnerability
- Functional devastation: occupational impairment, academic failure (especially in childhood-onset), social isolation, relationship breakdown, family accommodation
- Physical complications: dermatitis from excessive washing, excoriation/alopecia from picking/pulling, nutritional deficiency from eating rituals, iatrogenic medication effects
- Chronic course: rarely remits if untreated (~20% in 40 years); even treated, ~40% remission at 15 years; relapse common after medication discontinuation
- Treatment resistance: 30–40% fail adequate trials; may require escalation to neurosurgical interventions
- Insight deterioration: can progress from good to absent/delusional over time → resembles psychosis → therapeutic challenge
- Family impact: accommodation by family members paradoxically reinforces the OCD cycle
- Special populations: perinatal OCD (harm obsessions about baby — do NOT confuse with postpartum psychosis); clozapine can worsen OCD in schizophrenia patients
Active Recall - Complications of OCD
References
[1] Lecture slides: GC 171. Stress-related disorders and obsessive-compulsive disorder (Post-traumatic stress disorder adjustment disorder, acute stress disorder)_rev.pdf (p35) [3] Senior notes: ryanho-psych.md (Section 8.2 Obsessive-Compulsive Disorder — Course and Prognosis, pp. 188–190) [5] Lecture slides: GC 171 (p38) — Co-morbidities of OCD [24] Lecture slides: GC 171 (p43) — Summary
High Yield Summary
- Definition: Obsessions ± compulsions that are CORE — Compulsion (driven), Own thoughts, Resistance, Ego-dystonic
- Epidemiology: ~2% prevalence; mean onset 19.5y; 25% by age 14; M=F in adults but M earlier onset; rarely remits untreated (~20% in 40y)
- Comorbidities: > 70% anxiety disorders; > 60% mood disorders (MDD most common); up to 30% tic disorders; 12% schizophrenia/schizoaffective
- Neurocircuitry: Hyperactive orbitofrontal CSTC loop (OFC → caudate → thalamus → OFC); ↑ activity in OFC, caudate, ACC, thalamus on functional imaging
- Aetiology: Genetics (SLC1A1 glutamate transporter most consistent), serotonergic dysfunction, CSTC loop, PANDAS (autoimmune), cognitive factors (inflated responsibility), stress/hormonal triggers
- Clinical Features: Obsessions (ruminations, impulses, images, doubts, phobias) and compulsions (checking, cleaning, counting, slowness, mental rituals); maintained insight; presence of resistance; anxiety as primary affective response; avoidance behaviour; frequent comorbid depression
- Key distinction from OCPD: OCD = ego-dystonic, ritualistic compulsions; OCPD = ego-syntonic, perfectionism without true obsessions/compulsions
- Prognostic factors: Worse with childhood onset, tic-related, male, poor insight/overvalued ideas, comorbid depression, personality disorder
High Yield Summary
- Always rule from the top of the diagnostic hierarchy downward: Organic → Substance → Psychotic → Mood → OCD → Personality
- The ego-dystonic test: OCD obsessions are ego-dystonic (senseless, unwanted); GAD worries are ego-syntonic; OCPD traits are ego-syntonic
- The ownership test: OCD thoughts are recognised as own; in psychosis with thought insertion, thoughts feel alien/externally imposed
- The content domain test: OCD has broad obsessional themes; BDD is limited to appearance; trichotillomania has no obsessions; hoarding is about difficulty discarding
- The trauma link test: PTSD intrusions are trauma-related; OCD intrusions are unrelated to specific trauma
- The purpose test: Compulsions aim to neutralise obsessions; tics are purposeless and preceded by sensory urges not cognitive obsessions
- Insight spectrum in OCD: Good/fair → poor → absent/delusional; absent insight OCD can mimic delusional disorder — look for characteristic OCD themes and absence of other psychotic features
- OCD and comorbidity: > 70% anxiety disorders, > 60% mood disorders, up to 30% tic disorders, 12% schizophrenia/schizoaffective — always screen for comorbidities
High Yield Summary
- OCD is a clinical diagnosis — no blood test or scan confirms it. The clinical interview IS the investigation.
- DSM-5 Criterion A: Obsessions (intrusive, unwanted, cause distress + attempts to suppress/neutralise) and/or Compulsions (repetitive, driven, aimed at reducing distress but not realistically connected or clearly excessive)
- DSM-5 Criterion B: Time-consuming ( > 1 hour/day) OR clinically significant distress/impairment
- DSM-5 Criterion C: Not attributable to substance or medical condition
- DSM-5 Criterion D: Not better explained by another mental disorder
- Specifiers: Insight (good/fair, poor, absent/delusional) and Tic-related
- ICD-10 key differences: Requires ≥ 2 weeks duration; explicitly requires ownership of thoughts, resistance, and non-pleasurability; applies diagnostic hierarchy more strictly
- Y-BOCS is the gold standard severity scale (0–40; subclinical < 8, mild 8–15, moderate 16–23, severe 24–31, extreme 32–40)
- Screening question: "Do you get thoughts stuck in your head that really bother you, or need to do things over and over like washing your hands, checking things, or counting?"
- Organic workup is only needed in atypical presentations: ASOT for PANDAS, MRI for basal ganglia lesions, EEG for TLE, drug screen for substances
- Pre-treatment: ECG (especially before clomipramine or high-dose SSRI), LFTs, U&Es, TFTs, pregnancy test
High Yield Summary
- Stepped care: 1st line = SSRI or intensive CBT → 2nd line = SSRI + CBT → 3rd line = clomipramine → 4th line = add antipsychotic or clomipramine + citalopram
- SSRIs: First-line pharmacotherapy; require higher doses than depression (max tolerated dose); 8–12 weeks to assess response; continue ≥ 1–2 years after remission then slow taper
- Clomipramine: Most potent SRI; reserved for SSRI failure; significant side effects (anticholinergic, cardiac, lethal in overdose); ECG mandatory
- Antipsychotic augmentation: For partial/non-responders; risperidone and aripiprazole have best evidence; especially useful in tic-related and poor-insight OCD
- CBT with ERP: Gold-standard psychotherapy; ~2/3 improve; works by blocking compulsion → allowing habituation → breaking obsession-anxiety-compulsion cycle; less effective for pure obsessions without rituals
- Cognitive therapy: Targets inflated responsibility, thought-action fusion, magical thinking; enhances ERP effect when combined
- Both CBT and SSRIs normalise CSTC loop hyperactivity — CBT reduces right caudate hyperactivity in treatment responders
- Anxiolytics: Short-term only (≤ 2–4 weeks); bridge therapy; do NOT treat core pathology; impair CBT learning
- Neurosurgery: DBS (reversible, ~60% response) or psychosurgery (irreversible, ~30–50% response) for treatment-refractory cases only
- Treatment response rate: 40–60% overall; complete remission less common → importance of combination and augmentation strategies
- Key side-effect vigilance: QTc (clomipramine, high-dose SSRI), serotonin syndrome (SSRI + clomipramine), initial anxiety worsening with SSRI initiation
High Yield Summary
- Depression is the single most common complication: > 60% lifetime mood disorder (MDD most common); arises from chronic distress, functional impairment, and shared serotonergic pathology; worsens prognosis
- Suicidality is significantly elevated: ~63% lifetime ideation, ~26% attempts; driven by comorbid depression, hopelessness, shame, treatment resistance, and absent insight
- Anxiety disorder comorbidity: > 70% lifetime; shared circuitry and genetic vulnerability
- Functional devastation: occupational impairment, academic failure (especially in childhood-onset), social isolation, relationship breakdown, family accommodation
- Physical complications: dermatitis from excessive washing, excoriation/alopecia from picking/pulling, nutritional deficiency from eating rituals, iatrogenic medication effects
- Chronic course: rarely remits if untreated (~20% in 40 years); even treated, ~40% remission at 15 years; relapse common after medication discontinuation
- Treatment resistance: 30–40% fail adequate trials; may require escalation to neurosurgical interventions
- Insight deterioration: can progress from good to absent/delusional over time → resembles psychosis → therapeutic challenge
- Family impact: accommodation by family members paradoxically reinforces the OCD cycle
- Special populations: perinatal OCD (harm obsessions about baby — do NOT confuse with postpartum psychosis); clozapine can worsen OCD in schizophrenia patients
Anxiety Disorders
Anxiety disorders are a group of mental health conditions characterized by excessive, persistent fear or worry that is disproportionate to the actual threat and causes significant functional impairment.
Somatoform Disorders
Somatoform disorders are a group of psychiatric conditions characterized by the presence of physical symptoms that cannot be fully explained by a general medical condition, substance use, or another mental disorder, causing significant distress or functional impairment.