Taking this into consideration, we aimed to evaluate the role of BDNF, CREB1, NTRK2, NGFR, ARC, GSK3B, AKT, MAPK1, MTOR, PTEN, and SYN1 genetic polymorphisms in AD treatment phenotypes in a cohort of Portuguese MDD patients. The gene discussed is SYN1; the disease is major depressive disorder.