Obsessive compulsive disorder is characterised by the presence of obsessions and/or compulsions.

It is a relatively common disorder with a wide clinical spectrum. It may significantly impact an individual's daily life and be a cause of profound functional impairment.

NICE reports that anywhere between 1-3% of the UK population are affected. It is characterised by two features:

  • Obsessions: intrusive thoughts, urges and images that cause anxiety and distress.
  • Compulsions: repetitive behaviours that one feels compelled to perform, these may be observable or occur in the mind (e.g. repeating a phrase).


OCD is a leading cause of global disease burden.

It is estimated that OCD affects 1-3% of the UK population.

It has been observed that childhood OCD affects boys more frequently than girls. After puberty, this appears to reverse. The overall gender balance is roughly equal.

Risk factors

As with many mental health illnesses the aetiology is poorly understood but likely multifactorial.

A number of risk factors have been identified. 

  • Family history
  • Age (onset normally between 10-21)
  • Emotional/stress triggers
  • Pregnancy and post-natal period
  • Childhood abuse and neglect

Features of OCD may rarely be a symptom secondary to another neurological condition.


The diagnosis of OCD is clinical, classification systems may be used to support this.

Diagnosis of OCD can be challenging. Some patients may feel embarrassed or ashamed by features of the disease and may not wish to discuss their symptoms. Clinicians must pick up on signs and foster an open and honest dialogue.

Those particularly at risk should be screened for:

  • Anxiety/depression
  • Substance misuse
  • Body dysmorphia
  • Anorexia nervosa

NICE advise the following questions to help screen for the diagnosis:

  • Do you wash or clean a lot?
  • Do you check things a lot?
  • Is there any thought that keeps bothering you that you would like to get rid of, but cannot?
  • Do your daily activities take a long time to finish?
  • Are you concerned about putting things in a special order, or are you upset by mess?
  • Do these problems trouble you?

The diagnosis is made with clinical judgment and can be helped by either ICD-10 or DSM-V classifications. Below we outline the DSM-V criteria:

  1. Obsessions, compulsions or both.
  2. Obsessions or compulsions cause distress and are time consuming (>1hr / day) or interfere with normal day to day life.
  3. Obsessions or compulsions are not attributable to another condition, medication or substance.
  4. Obsessions or compulsions are not better explained by another mental health illness.

Differential diagnosis

A number of conditions closely match and overlap with features of OCD.

  • Obsessive-compulsive personality disorder
  • Autism spectrum disorder
  • Body dysmorphic disorder
  • Delusional disorder
  • Substance-induced OCD
  • Medication-induced OCD
  • Trichotillomania


OCD treatment often involves psychological therapies and the use of SSRIs.

Once a diagnosis is made, discuss the condition and its management in detail with the patient. Ensure they are aware of the numerous charities and support groups available (see further reading below).

OCD is often a chronic condition, and close follow-up is required. The natural history may feature periods of improvement and periods of worsening symptoms. Some undergo remission and many will find their symptoms improve with treatment and time.

Evaluate severity

Severity is largely dictated by the distress caused by each individual feature and how it limits their normal function.

In some cases, certain aspects may raise concerns of risk of harm for the patient and to others. Safeguarding concerns must be addressed. Expert opinion should be sought where concern exists.

Consider and assess suicide and self-harm risk. Any patient deemed to be at risk should be discussed immediately with the local specialist mental health services for further assessment and a management plan.

You should be aware that OCD may co-exist with other mental health disorders. Attempt to evaluate and screen for these.


Mild functional impairment: refer for psychological intervention. Low-intensity Cognitive-Behavioural Therapy (CBT) with Exposure and Response Prevention (ERP) is commonly offered. If treatment is inadequate or inappropriate consider the option for moderate functional impairment.

Moderate functional impairment: patients should be offered intensive CBT with ERP or an SSRI. Clomipramine may be used as second-line therapy. If treatment is inadequate or there are concerns regarding the assessment, refer for specialist input.

Severe functional impairment: refer for specialist input. Consider an SSRI (e.g escitalopram) combined with CBT in the interim. Clomipramine may be used as second-line therapy.

Specialist referral

Specialist referral should be considered in any patient in whom you have concern. In particular, patients who exhibit marked limitation of normal function should be referred. Refer those at risk of self-harm, neglect or significant co-morbidities. Suicide risk should be assessed and urgently referred (same day) if any concern exists.

Further reading

A number of mental health charities exist that help provide information and support for patients.

  • MIND: a mental health charity, provides information on OCD (and other mental health illnesses).
  • OCD UK: a national charity for OCD that provides support for those with OCD, raises funds and spreads awareness.
  • Perinatal OCD: useful information for patients and family regarding perinatal OCD.
  • NICE guidelines CG 31: first published in 2005, note that it is due an update to better reflect current practice.

Last updated: March 2021
Author The Pulsenotes Team A dedicated team of UK doctors who want to make learning medicine beautifully simple.

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