HTR2A and major depressive disorder: RSP is an atypical antipsychotic, with predominant antagonist effects at DA D2/3 and 5HT2 receptors (Leysen et al. 1994), which, like other atypical antipsychotics, is effective as adjunctive therapy for treatment-resistant depression (Wright et al. 2013) and as monotherapy in bipolar disorder (Lindström et al. 2017).