Linking Environmental Exposures to Depression: Insights from Epidemiology, Biology, and Methodology

Depression is a leading cause of disability worldwide, with significant personal and societal consequences. Emerging research highlights the critical role of environmental exposures as modifiable risk factors influencing depression risk and progression. Over the past decade, a substantial body of epidemiological evidence has linked diverse environmental factors—including air pollution, limited green space access, chronic noise exposure, adverse features of urbanization, unhealthy lifestyle behaviors, early life adversity, and internal toxicant burdens—to elevated risks of depressive symptoms and clinical depression. These exposures exert their effects through interconnected biological pathways, including chronic systemic inflammation, oxidative stress, hypothalamic-pituitary-adrenal axis dysregulation, blood-brain barrier disruption, and gut microbiota alterations. Recent methodological advances, such as high-resolution environmental exposure assessment, multi-exposure model approaches, longitudinal cohort designs, and enhanced causal inference techniques, have strengthened the evidence base. Nevertheless, challenges remain in accurately characterizing multifactorial exposures and establishing causal relationships across diverse populations. Incorporating a life course perspective and adopting comprehensive exposome frameworks will be essential for future research. Understanding environmental determinants of depression not only advances etiological knowledge but also highlights critical opportunities for prevention. Public health interventions aimed at reducing harmful environmental exposures, enhancing urban green infrastructure, promoting healthy lifestyle behaviors, and mitigating psychosocial stressors offer promising strategies for reducing the burden of depression. Ultimately, integrating environmental health perspectives into mental health research and policy may provide transformative approaches to preventing and alleviating depression at the population level.