A Cochrane review included 11 RCTs with a total of 396 participants with obsessive compulsive disorder (OCD). In all trials the diagnosis of OCD was done according to DSM-IV. Also, in all trials antipsychotic, olanzapine, quetiapine or risperidone, and placebo treatment was given as adjunctive therapy to antidepressive treatment with mainly SSRIs, but also SNRIs or clomipramine. The duration of all trials was less than 6 months, 13% of the participants left the trials early. When olanzapine and placebo were compared there was no difference in the primary outcome, response to treatment (OR 0.28; 95% CI 0.01 to 6.45) or most other efficacy-related outcomes, but olanzapine was associated with more weight gain than monotherapy with antidepressants (2 trials, n=70). Quetiapine was not more efficacious than placebo in terms of the primary outcome, response to treatment (OR 0.53; 95% CI 0.27 to 1.05; 5 RCTs, n = 219), but there was a significant superiority in the mean Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score at endpoint (MD -2.28, 95% CI -4.05 to -0.52; 5 RCTs, n = 219). There were also some beneficial effects of quetiapine in terms of anxiety or depressive symptoms. Risperidone was more efficacious than placebo in terms of the primary outcome (number of participants without a significant response) (OR 0.17, 95% CI 0.04 to 0.66; 3 RCTs, n = 92) and in the reduction of anxiety and depression (MD -7.60, 95% CI -12.37 to -2.83; one RCT, n = 36).
Comment: The quality of the evidence is downgraded by study quality (unclear allocation concealment, short follow-up time) and imprecise results (few patients with wide confidence intervals).