Obsessive-compulsive disorder (OCD) is an anxiety disorder characterized by recurrent, unwanted thoughts (obsessions) and/or repetitive behaviors (compulsions). People with OCD feel they cannot control these obsessions and compulsions. Repetitive behaviors such as hand washing, counting, checking, or cleaning are often performed in the hopes of reducing anxiety or anxiety-provoking obsessions. Performing these so-called rituals, however, provides only temporary relief. Left untreated, the obsessions and compulsions can take over a person's life. OCD is often a chronic, relapsing illness.

The cause of OCD is not known. It is believed to develop from genetic, biologic, environmental, and psychologic factors.

OCD may be associated with other disorders, including:

  • Tourette syndrome – characterized by multiple motor and vocal tics
  • Trichotillomania – the repeated urge to pull out scalp hair, eyelashes, eyebrows, or other body hair
  • Body dysmorphic disorder – imaginary or exaggerated defects in appearance
  • Eating disorders – such as bulimia nervosa or anorexia nervosa
  • Hypochondriasis – morbid concern for one's own health, including delusions that one is suffering from a disease or diseases for which no physical basis is evident
  • Substance abuse

Additional disorders that may accompany OCD include depression , attention-deficit hyperactivity disorder (ADHD) , and other anxiety disorders.

Approximately 3.3 million American adults have OCD during the course of a given year. The first symptoms of OCD often begin during childhood, adolescence, or early adulthood.