By John M. Grohol, Psy. Browse through our comprehensive listing of OCD resources .
Obsessions are unwanted ideas or impulses that repeatedly pop up in a person's mind.
These thoughts are often intrusive, unpleasant, and produce a high degree of anxiety. Sometimes the obsessions are of a violent or a sexual nature, or concern illness. Compulsions , on the other hand, are repetitive behaviors which people who suffer from OCD resort to. A person who has OCD often believes that these behaviors will keep harm away from them or their loved ones and that if they fail to complete a compulsive behavior, harm is imminent. Co-existing disorders can make OCD more difficult both to diagnose and to treat.