Antidepressants that enhance both serotonergic and noradrenergic neurotransmission may be more effective than selective serotonin reuptake inhibitors (SSRIs) for acute-phase therapy of major depressive disorder. As a noradrenergic and specific serotonergic antidepressant, the antidepressive mechanism of mirtazapine is quite superior to SSRI and in particular has been suggested to have a faster onset of action than SSRIs in MDD patients.