Who is affected and when does it start?

The onset of OCD is in usually in adolescence or early adulthood. Nearly one half of all cases begin in childhood and it is rare to see onset after age 35 years. In adults with OCD, men and women are almost equally affected by OCD. This contrasts with both depression and panic disorder, two disorders with a clear preponderance of women. In childhood OCD, boys outnumber girls and their age of onset is earlier. Studies from the National Institute of Mental Health (NIMH) suggest that very early onset (before age 7 years) OCD in boys may be related to Tourette's Syndrome (TS), a disorder involving multiple sudden, involuntary movements called tics.

OCD strikes people from all walks of life and all levels of educational background. Factors that predispose one to develop OCD have not been identified. Strict religious training is thought to shape the content of one's obsessions (i.e., increased concerns with scruples and sacrilege), but has not been shown to increase the likelihood of developing OCD.

There are few modifications needed for making the diagnosis of OCD in childhood. The clinical presentation in children and in adults is remarkably similar. While most children recognize that the symptoms are unwanted, it may be more difficult to evaluate insight in younger children with OCD. Not all rituals in childhood should be considered pathological. A need for sameness and consistency may promote a sense of security at times of transition. For example, many normal children engage in bedtime rituals such as arranging their bedding in a particular way, ensuring that their toes are covered, or checking for "monsters" under the bed. Childhood rituals should be suspected as signs of OCD when they become maladaptive (i.e., time-consuming or distressing) and persistent.