http://www.nimh.nih.gov/health/topics/obsessive-compulsive-disorder-ocd/index.shtml
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National Institute of Mental Health, National Institutes of Health
Obsessive-Compulsive Disorder, OCD, is an anxiety disorder and is characterized by recurrent, unwanted thoughts (obsessions) and/or repetitive behaviors (compulsions). Learn about signs and symptoms, treatment, and where to get help.