Obsessive Compulsive Disorder (OCD) is an anxiety disorder characterized by unwanted and persistent thoughts (obsessions) that lead to repetitive behaviors (compulsions) like excessive cleaning, counting, or checking. The exact causes are unknown but likely involve brain dysfunction and genetic factors. Symptoms include obsessions over germs, dirt or causing harm as well as compulsions like hand washing, cleaning, or counting. OCD is diagnosed by a mental health professional through evaluation and cannot be diagnosed through medical tests. Treatment involves therapy with a mental health professional and sometimes medication.