The under-recognized role of dopamine in the treatment of major depressive disorder.

Major depressive disorder (MDD) is currently the second most common cause of disability worldwide. Current treatment of MDD with selective serotonin reuptake inhibitors and serotonin-noradrenaline reuptake inhibitors is limited by efficacy and tolerability issues, highlighting the unmet need in the treatment of patients with MDD. Deficiencies in dopamine, serotonin and noradrenaline are thought to underpin MDD pathophysiology. Atypical antipsychotics, which modulate these receptor systems, may provide additional treatment options. This article assesses the current treatment options available for patients with MDD and considers possible future therapies. The potential role of atypical antipsychotics such as olanzapine, risperidone and quetiapine in the treatment of MDD is explored based on evidence from bipolar depression trials and preliminary studies in patients with MDD.