As their name indicates, SSRIs, currently the most used AD, possess much higher selectivity for the 5-HT transporter (SERT) than for the transporters of norepinephrine (NET) and dopamine (DAT), and were developed after the serotonergic theory of depression postulated by Lapin and Oxenkrug (23) which suggests that serotonergic pathways play a major role in depression. The gene discussed is SLC6A4; the disease is depressive disorder.