Genetic and Epigenetic Insights in Major Depression

Abstract

Clinical Depression is a prevalent, disabling psychiatric disorder with rising global impact,
especially in low- and middle-income countries. Traditionally defined by affective and
cognitive symptoms, Major Depressive Disdorder is now understood as a heterogeneous
disorder influenced by both biological and environmental factors. This review explored the
neurobiological and genetic foundations of MDD, emphasizing key molecular pathways
including serotonergic signaling, neuroinflammation, neurotrophic support, and stress
reactivity. Candidate genes such as SLC6A4, BDNF, and FKBP5 are examined, alongside
emerging insights into gene-environment interactions (G×E) and epigenetic modulation of
depression risk. This review also discussed recent advances in polygenic risk scoring,
microbiota-brain interactions, and immune-metabolic frameworks that are reshaping
understanding of depression etiology. Special attention is given to the underrepresentation of
African populations in psychiatric genetics, highlighting the importance of diversity in
biomarker discovery and treatment development. The review advocated for a systems-based,
integrative approach that accounts for sex differences, environmental context, and genomic
variability. Future research directions include the use of multi-omics, culturally inclusive study
designs, and biomarker-informed strategies for prevention and treatment. By bridging
neurobiology with real-world diversity, this review underscores the importance of translational
psychiatry in addressing the evolving global burden of MDD.