Intrusive thought
Antidepressants which have been shown to be effective in treating OCD include fluvoxamine (trade name Luvox), fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), citalopram (Celexa), and clomipramine (Anafranil). Although SSRIs are known to be effective for OCD in general, there have been fewer studies on their effectiveness for intrusive thoughts. A retrospective chart review of patients with sexual symptoms treated with SSRIs showed the greatest improvement was in those with intrusive sexual obsessions typical of OCD. A study of ten patients with religious or blasphemous obsessions found that most patients responded to treatment with fluoxetine or clomipramine. Women with postpartum depression often have anxiety as well, and may need lower starting doses of SSRIs; they may not respond fully to the medication, and may benefit from adding cognitive behavioral or response prevention therapy.
Biology of obsessive–compulsive disorder
Abnormal affect in OCD has been hypothesized to result from dysfunction in the OFC, ventral striatum, and amygdala. OCD is characterized by high levels of anxiety, high rates of comorbidity with major depressive disorder, and blunted response to reward. This is reflected by reduced amygdala and ventral striatum response to positive stimuli, and elevated amygdala response to fearful stimuli. Furthermore, deep brain stimulation of the nucleus accumbens is an effective treatment of OCD, and symptom improvement correlates with reduced binding of dopamine receptors. The reduced binding, due to the ability of the radioligand tracers to be displaced by endogenous dopamine, is taken to reflect increased basal dopamine release. Affective dysregulation due to blunted reward, and elevated fear sensitivity may promote compulsivity by assigning excessive motivational salience to avoidance behavior.