Antipsychotics as antidepressants.

Three second-generation antipsychotic (SGA) agents have received FDA approval for adjunctive treatment, to antidepressant, of major depressive disorder: quetiapine, aripiprazole, and olanzapine. Additionally, quetiapine and lurasidone have been approved for the treatment of bipolar depression. There are data suggesting that quetiapine is effective for major depressive disorder as monotherapy. These agents are effective for depression only at subantipsychotic doses. Receptor profiles predict that all SGA will have anxiolytic effects as subantipsychotic doses but that all will be dysphorogenic at full antipsychotic doses (i.e., produce a depression-like clinical picture). The antidepressant effect appears to be unique to some agents, with direct evidence of insignificant antidepressant action for ziprasidone. Three general principles can guide the use of antipsychotics as antidepressants: (i) All SGAs may have anxiolytic effects; (ii) full antipsychotic doses are dysphorogenic, and therefore, subantipsychotic doses are to be used; and (iii) SGAs do not have a general antidepressant effect, rather, this appears to be unique to quetiapine and aripiprazole, and possibly lurasidone.