Obsessive-compulsive disorder (OCD) is an anxiety state marked by recurrent, unwanted thoughts or images (obsessions) and unwanted repetitive behaviors (compulsions).

Common obsessions include:

• fear of contamination from germs
• thoughts of aggressive behavior
• fear of harming oneself.

Common compulsions include:

• rechecking locked doors
• repetitive hand washing
• excessive neatness.

People who suffer from OCD recognize that their obsessions and compulsions are unreasonable but they cannot resist the intruding thoughts or ritualistic behavior. Symptoms, which usually first appear in the teens or 20s, are often severe enough to interfere with daily functioning. 

People with OCD do not necessarily have both obsessions and compulsions; either one is sufficient for a diagnosis. Though previously considered rare, OCD is now estimated to affect 2 to 3 percent of the population.