Obsessive–compulsive disorder (OCD) is a mental disorder in which a person feels the need to perform certain routines repeatedly (called "compulsions"), or has certain thoughts repeatedly (called "obsessions"). The person is unable to control either the thoughts or activities for more than a short period of time.Obsessive-Compulsive Disorder (OCD) is a common, chronic, and long-lasting disorder in which a person has uncontrollable, reoccurring thoughts (obsessions) and/or behaviors (compulsions) that he or she feels the urge to repeat over and over.

It is believed that OCD likely is the result of a combination of neurobiological, genetic, behavioral, cognitive, and environmental factors that trigger the disorder in a specific individual at a particular point in time. ... People with severe OCD symptoms may have a second variation in the same gene.

Common obsessive thoughts in OCD include:

Fear of losing control and harming yourself or others. Intrusive sexually explicit or violent thoughts and images. Excessive focus on religious or moral ideas. Fear of losing or not having things you might need.If left untreated, OCD can worsen to the point that the sufferer develops physical problems, becomes unable to function, or experiences suicidal thoughts. About 1% of OCD sufferers die by suicide.