Obsessive-compulsive disorder (OCD) is a type of anxiety disorder. If you have OCD, you have frequent, upsetting thoughts called obsessions. To try to control the thoughts, you feel an overwhelming urge to repeat certain rituals or behaviors. These are called compulsions.
Examples of obsessions are a fear of germs or a fear of being hurt. Compulsions include washing your hands, counting, checking on things, or cleaning. With OCD, the thoughts and rituals cause distress and get in the way of your daily life.
Researchers think brain circuits may not work properly in people who have OCD. It tends to run in families. The symptoms often begin in children or teens. Treatments include therapy, medicines, or both. One type of therapy, cognitive behavioral therapy, is useful for treating OCD.
NIH: National Institute of Mental Health