Double-blind randomised controlled trials (RCTs) that compared adjunctive atypical antipsychotic agents with placebo in patients with non-psychotic unipolar major depressive disorder were eligible for inclusion. Patients had to have non-psychotic major depressive disorder that was resistant to prior antidepressant treatment determined by either history or a prospective trial. Outcomes included response (defined as an improvement of at least 50% from baseline to endpoint on either the Hamilton Depression Rating Scale or Montgomery-Asberg Depression Rating Scale), remission and rates of discontinuation.
In the included trials, atypical antipsychotic agents comprised olanzapine, risperidone, quetiapine, and aripiprazole. Antidepressants included fluoxetine, various agents and serotonin re-uptake inhibitors/serotonin noradrenaline re-uptake inhibitors. Duration of the included trials ranged from four to 12 weeks; nearly all were between six and eight weeks.
The authors did not state how the papers were selected for review, or how many reviewers performed the selection.