Author(s)

Ruofan Zhang

Corresponding Author

Ruofan Zhang

Abstract

Depression affects about 5% of the global population and presents substantial heterogeneity in symptoms and treatment response. This literature review summarizes major depressive disorder (MDD) subtypes and focuses on genetic contributions to depression susceptibility, emphasizing 5-HTT and BDNF. The short allele of a 5-HTT polymorphism has been linked to reduced transcriptional activity and lower transporter expression and may increase vulnerability to depressive outcomes following stressful life events. The BDNF Val66Met polymorphism, particularly the Met allele, has been associated with altered activity-dependent BDNF secretion and neuroplasticity, potentially influencing depression risk and treatment response. Overall, findings support a multifactorial gene–environment framework.

Keywords

Depression; Major depressive disorder; 5-HTT; BDNF; Val66Met; Gene–environment interaction