Abstract: Etiology and pathophysiology of obsessive compulsive disorder remains inconclusive till today. Multiple converging lines of evidence suggest that neurobiology plays a significant role in the etiology of obsessive compulsive disorder (OCD). Certain brain areas frequently involved in symptomatology of OCD, analyzed by neuroimaging studies. The strongest pharmacologic evidence concerns the serotonergic system and the well-established efficacy of potent serotonin reuptake inhibitors in the treatment of OCD. Cholesterol forming the vital component of neurons regulates neurochemical activity. Reduced serum cholesterol level causes hyperactivity of serotonin reuptake receptor activity precipitating symptoms of OCD.