Obsessive Compulsive Disorder affects 1.2% of the population – roughly 12 out of every 1000 people have OCD. One of the most common forms of OCD is excessive doubt that causes repeated, often irrational, checking. Most people with OCD have a self-imposed sense of responsibility to prevent harm and an exaggerated perception of the threats that their intrusive thoughts indicate. A quarter of OCD sufferers have an uncontrollable fear of getting a disease through contamination, which causes them to repeatedly wash and refuse to touch certain objects that are perceived as dirty. Some people with OCD worry about religious matters, inappropriate sexual thoughts, and attraction to members of the same sex. People with another form of OCD may have thoughts of harming themselves and others.