Mental Health

Obsessive-compulsive disorder

A disorder of intrusive obsessions and repetitive compulsions that briefly reduce distress but maintain the cycle and impair daily life.

In a nutshell

OCD is defined by distressing intrusive obsessions and/or compulsions that consume time or impair function. The treatment anchor is CBT with exposure and response prevention; adult treatment intensity follows functional impairment, and severe illness generally needs combined CBT/ERP and an SSRI.

Classic presentation

Intrusive contamination, harm, symmetry or taboo thoughts with washing, checking, ordering, counting, mental rituals or reassurance-seeking that briefly relieve distress but recur and impair daily life.

Key points

Obsessions are unwanted and distressing; compulsions may be behavioural or mental and are often maintained by brief relief.
ERP is the core psychological treatment: graded exposure is paired with preventing the ritual and other neutralising responses.
For adults, use stepped care: low-intensity CBT/ERP for mild impairment, a choice of intensive CBT/ERP or an SSRI for moderate impairment, and combined treatment for severe impairment.
For children and young people, CBT including ERP should involve family or carers and be adapted to developmental age; SSRI decisions require specialist assessment and careful monitoring.
An SSRI trial may take up to 12 weeks to show benefit; monitor early for agitation, akathisia, suicidal thoughts or self-harm and taper rather than stop abruptly.
Harm-themed intrusive thoughts are usually ego-dystonic, but clinicians must still assess genuine intent, suicide risk, depression and safeguarding directly.
After adequate SSRI, combined CBT/ERP plus SSRI and clomipramine trials without response, refer to a specialist OCD multidisciplinary team.

First-line investigation

Clinical formulation of obsessions, compulsions, mental rituals, insight, impairment, comorbidity and risk; use a validated severity measure such as Y-BOCS as an adjunct and do targeted tests only for suspected alternatives.

Management

Assess impairment and risk

Characterise overt and covert rituals, functional impact, insight, family accommodation, depression, suicidality, genuine intent and safeguarding; use a severity measure to support the formulation.^2,1

Start CBT with ERP

Offer low-intensity CBT/ERP for mild adult impairment and more intensive CBT/ERP as impairment increases; grade exposures collaboratively and prevent compulsions and neutralising strategies.^2,3

Add medication when indicated

For moderate adults offer a choice of intensive CBT/ERP or an SSRI; for severe adult impairment combine CBT/ERP and an SSRI, using current BNF prescribing and monitoring advice.^2,4

Adapt treatment for children and young people

Use family/carer-involved, developmentally adapted CBT/ERP; if an SSRI is needed after specialist review, use it with concurrent CBT/ERP and careful early monitoring.^2,4

Review non-response and escalate

After adequate SSRI, combined CBT/ERP plus SSRI and clomipramine trials without response, refer to a specialist OCD multidisciplinary team; do not start augmentation casually in primary care.^2,4

Exam traps

Reassurance-seeking can be a compulsion and repeated reassurance can maintain the cycle.
A distressing intrusive thought of harming someone is not the same as intent, but risk must be assessed rather than assumed away.
ERP prevents the ritual; simply discussing whether the feared outcome is objectively possible is not an adequate substitute.
Severe adult functional impairment generally warrants combined CBT/ERP and SSRI treatment.
In children and young people, medication should not be treated as routine first-line monotherapy; follow NICE specialist and monitoring requirements.

Illustrations

Cortico-striato-thalamo-cortical loop in OCDDiagram of the orbitofrontal cortex–striatum–thalamus loop, showing the error-detection signal proposed to contribute to obsessions in OCD.PassFinals · original

The obsession–compulsion reinforcement cycleDiagram showing how a compulsion briefly reduces distress, reinforcing the ritual while the obsession and uncertainty return.PassFinals · original

Exposure and response prevention principleIllustration of a graded ERP hierarchy showing exposure to a trigger while reducing the compulsive response and other neutralising strategies.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.