<prompt> 25 yr old gentleman has repeated thoughts that he has not locked his car door properly, frequently checks it while driving, he repeatedly checks locks in his house. DiagnosisOCDOPCDPhobiaPersonality disorder  <response>: Obsessive Compulsive Disorder : Obsession: recurrent and persistent thoughts that are involuntary unwanted, distressing and the individual tries to neutralize them by a thought or action compulsion. Ex: Contaminationmost common, Need for symmetry, Pathological doubt, Sexual compulsion: Act aimed to reduce the anxiety arising out of obsession but fails to do so. Ex: checkingmost common, washing, counting, Hoarding, counting. obsession a door is unlocked leads to compulsion checking , which tries to relieve distress but fails and the obsession-compulsion cycle repeats leading to distress, time consumption. thoughts are ones own thoughts, it may be an ideaurgeimage -behavior or mental behavior. M:F- 1:1 age of onset 20-25 years 2-3 prevalence in general population Comorbidity: major depressive disorder, delusional beliefs, overvalued ideas, personality disorder Etiology Psychoanalytical concept-regression from the oedipal phase to the anal psychosexual phase. Anatomical- altered function in the connections between orbitofrontal coex, caudate, thalamus. Biochemical-dysregulation of serotonin. Treatment : Pharmacotherapy-Selective serotonin Reuptake InhibitorsSSRI fluoxetine, fluvoxamine, paroxetine, seraline Tricyclic antidepressants TCAclomipramine Behavior therapy: Desensitization, thought stopping, flooding, implosion therapy, aversive conditioning Psychotherapy Surgical cingulotomy, capsulotomye.g., subcaudate tractotomy,. Nonablative surgical techniques like Deep Brain Stimulation of basal ganglia nuclei Reference: P.605 Kaplan Sadocks Synopsis of psychiatry clinical Psychiatry, 10th Edition16.4 