Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) causes people to have persistent, upsetting thoughts (obsessions) for which people use rituals (compulsions) to control the anxiety these thoughts produce. Common rituals include hand-washing, checking things, touching things in a particular order or counting things. Some common obsessions include having frequent thoughts of violence and harming loved ones, thinking about performing sexual acts the person dislikes, or having thoughts that go against one’s religious beliefs. People with OCD may also be preoccupied with order and symmetry, have difficulty throwing things out, or hoard unneeded items.
For More Information:

Adults:

http://www.nmha.org/go/information/get-info/anxiety-disorders/obsessive-compulsive-disorder-ocd

http://www.helpguide.org/mental/obsessive_compulsive_disorder_ocd.htm

Adolescents:
http://www.kidshealth.org/kid/health_problems/learning_problem/ocd.html