• Clinical science

Obsessive-compulsive disorder


Obsessive-compulsive disorder (OCD) is characterized by persistent and recurring thoughts, urges, or images (obsessions) that lead to repetitive behaviors or mental acts (compulsions). Since obsessions are experienced as intrusive and involuntary as well as undesirable and unpleasurable, they generally cause anxiety or distress. While compulsive actions are generally not experienced as pleasurable, their performance may provide relief from the distress and anxiety caused by an obsession. At the same time, however, compulsions are, like the obsessions that trigger them, uncontrollable as well as time-consuming and therefore cause distress and impairment of function. Comorbidity with anxiety, mood, and tic disorders is common. Therapy typically involves cognitive behavioral therapy (CBT) and selective serotonin reuptake inhibitors (SSRIs).


  • Sex:
  • Age of onset: average is 20 years of age
  • Lifetime prevalence: approx. 2%


Epidemiological data refers to the US, unless otherwise specified.


The etiology of OCD is multifactorial. Factors that have been associated with OCD development include:

  • Genetic: familial transmission (concordance rate of 0.57 in monozygotic twins)
  • Neurobiological: abnormalities in the orbitofrontal cortex, anterior cingulate cortex, and striatum
  • Serotonin level imbalance may play a role.
  • Infection: pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections (PANDAS)
  • Psychological trauma


Clinical features


  • Ego-dystonic: behavior or thought patterns that are inconsistent with or repulsive to one's sense of self
  • Obsessions: distressing thoughts, emotions, and/or sensations that are recurring and intrusive
  • Compulsions: repetitive actions to provide relief from anxiety caused by obsessions (can take up a substantial amount of time)




  • Diagnostic criteria (according to the DSM-5)
    • Obsessions and/or compulsions
      • Obsessions (e.g., thoughts about contamination, harm, or symmetry) defined by both:
        • Recurrent/persistent, intrusive thoughts, or urges that cause anxiety or distress
        • Attempts to suppress these thoughts or urges
      • Compulsions (e.g., repeatedly washing hands, opening and closing a door multiple times, or rearranging objects on a desk) defined by both:
        • Repetitive behaviors or mental exercises; (e.g., counting, repeating words) that the individual feels compelled to perform in order to relieve anxiety brought upon by the obsessions.
        • These behaviors or mental actions may be performed in an attempt to prevent some perceived dreaded event, though they tend to be excessive and not connected in any realistic way to the event.
    • Time-consuming (e.g., ≥ 1 hour/day), or result in significant distress/impairment (school, work)
    • Not due to substance-use disorders or another medical condition
    • Not due to another mental disorder (e.g., anxiety disorders, eating disorders)


Differential diagnoses

Differential diagnoses of obsessive compulsive disorder
Type of disorder Characteristics
Obsessive compulsive disorder
  • Intrusive thoughts, images, and urges that trigger repetitive, compulsive behavior
  • Ego-dystonic: behavior patterns are not in agreement with ideal self-image
Obsessive-compulsive personality disorder
  • Excessive perfectionism and rigid control regarding real-life concerns
  • Behavior is ego-syntonic, meaning that the affected individual's thought and behavior patterns are congruent with their self-image and therefore they do not perceive them as wrong.
Generalized anxiety disorder
  • Recurrent thoughts revolve around real-life concerns, e.g., work, as opposed to the obsessions in OCD, which tend to be of an irrational nature.
Hoarding disorder
  • Difficulty discarding belongings
Tic disorder
Body dysmorphic disorder
  • Compulsive behavior is limited to hair pulling in the absence of obsessions.

Hoarding disorder

  • Epidemiology
  • Diagnostic criteria (according to the DSM-5)
    • Persistent urge to keep items; distress associated with getting rid of items
    • Difficulty discarding belongings
    • Accumulation of belongings → intended use of belongings is compromised and living areas are cluttered
    • Clinically relevant impairment in functioning and/or clinically relevant distress
    • Not explained by other medical conditions (e.g., brain injuries) or mental illness (e.g.; , OCD)
  • Treatment

Body dysmorphic disorder

  • Definition: an excessive preoccupation with an imaginary or minor defect in a facial feature and/or body part
  • Epidemiology
  • Diagnostic criteria (according to the DSM-5)
    • Persistent preoccupation with a perceived flaw in one's physical appearance
    • Flaws are mild or not observable by others.
    • Repetitive behaviors (e.g., constantly checking the mirror, skin scratching) or thoughts about one's appearance (e.g., over-grooming, comparing oneself to others)
    • Clinically relevant impairments in functioning and/or clinically relevant distress
    • In order to conclusively diagnose BDD, an eating disorder that might also explain the symptoms should be ruled out.
  • Treatment

Trichotillomania (hair-pulling disorder)

The differential diagnoses listed here are not exhaustive.


A combination of pharmacotherapy and psychotherapy has been proven effective in the treatment of OCD.