Obsessive Compulsive Disorder (OCD) is a disorder where people experience unwanted and repetitive intrusive thoughts (obsessions) that lead them to feel compelled to perform repetitive behaviors or mental acts (compulsions). Common obsessions include fears of contamination or harm. Compulsions are rituals like excessive cleaning, counting, or checking performed to relieve the anxiety of the obsessions. OCD can be debilitating and is often treated with therapy and medication, though a complete cure can be difficult.