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Obsessive-Compulsive Disorder

A condition involving intrusive, unwanted thoughts, images or urges that cause marked distress, and repetitive behaviours or mental acts performed to reduce that distress or prevent a feared outcome.

Definition

OCD requires obsessions, compulsions, or both, that are time-consuming or cause significant distress or impairment.

Obsessions are recurrent intrusive thoughts, images or urges experienced as unwanted. Compulsions are repetitive behaviours or mental acts the person feels driven to perform, aimed at reducing distress or preventing something feared, and either not realistically connected to what they are meant to prevent or clearly excessive.

Mental compulsions — counting, reviewing, reassurance-seeking in one's own head — are compulsions, and missing them is a common assessment error.

History

Described in religious literature for centuries as scrupulosity. Classified with the anxiety disorders in earlier DSM editions and moved in DSM-5 into its own chapter, Obsessive-Compulsive and Related Disorders, alongside hoarding, body dysmorphic disorder, trichotillomania and excoriation.

That move is defensible on comorbidity and treatment-response grounds and is still argued about.

Theory

The cognitive-behavioural account is well specified and unusually well supported.

Intrusive thoughts are universal. Studies find that most people experience intrusive thoughts with content indistinguishable from clinical obsessions. What differs in OCD is the appraisal: interpreting the thought as significant, as revealing something about oneself, or as conferring responsibility to act.

The compulsion reduces distress in the short term and prevents disconfirmation in the long term, so it is negatively reinforced while maintaining the belief that produced it. Thought-action fusion — treating thinking something as morally equivalent to doing it, or as making it more likely — is a specific appraisal with good evidence.

Research

Lifetime prevalence around 1 to 2 percent, with no large gender difference overall, and typical onset in adolescence or early adulthood.

Exposure with response prevention is the treatment with the strongest evidence and outperforms medication alone. SSRIs at higher doses than for depression have evidence, and combination is used for severe presentations.

Delay to diagnosis is notoriously long, often more than a decade, particularly where the obsessions are taboo in content and the person has never told anyone.

Applications

The Yale-Brown Obsessive Compulsive Scale is the standard severity measure.

Assessment must ask directly about taboo obsessional content — harm, sexual and religious themes — because people rarely volunteer it, frequently believe it means something terrible about them, and are sometimes misdiagnosed as a risk when they are not.

Criticism

Harm obsessions are misread as risk. A person distressed by intrusive thoughts of harming someone is at low risk of doing so; the distress is diagnostic of OCD, not of danger. Misreading this causes real harm.
Treatment access is poor. Exposure with response prevention requires trained clinicians and many services do not have them.
The DSM-5 chapter reorganisation grouped conditions whose shared mechanism is asserted more than demonstrated.
Insight varies more than the criteria suggest, and poor-insight presentations respond less well.

References

Salkovskis, P. M. (1985). Obsessional-compulsive problems: A cognitive-behavioural analysis. Behaviour Research and Therapy, 23(5), 571-583.
Rachman, S., & de Silva, P. (1978). Abnormal and normal obsessions. Behaviour Research and Therapy, 16(4), 233-248.
Foa, E. B., et al. (2005). Randomized, placebo-controlled trial of exposure and ritual prevention. American Journal of Psychiatry, 162(1), 151-161.
Goodman, W. K., et al. (1989). The Yale-Brown Obsessive Compulsive Scale. Archives of General Psychiatry, 46(11), 1006-1011.

Written for PsychologyOrbit and reviewed before publishing. It is a summary for professionals and students, not clinical guidance, and it is not a substitute for the primary sources listed above.