Trauma and Depression

Trauma is a critical precipitating factor for major depressive disorder (MDD) as well as posttraumatic stress disorder (PTSD). This chapter reviews epidemiological evidence linking diverse traumatic events—including interpersonal violence, disasters, illness-related trauma, and war—to the onset of depression. High comorbidity between PTSD and MDD is consistently observed, explained by shared vulnerabilities such as genetic predisposition, early life adversity, and maladaptive stress responses. Particular attention is given to childhood trauma, which exerts long-lasting effects on brain development and stress regulation, thereby heightening vulnerability to adult depression through mechanisms involving 5-HTTLPR polymorphisms, hypothalamic–pituitary–adrenal axis dysregulation, and impaired neuroplasticity. Risk and protective factors are examined across developmental stages, emphasizing the roles of social support, family functioning, and coping self-efficacy. Recent global stressors—including climate change–related disasters and the coronavirus disease 2019 (COVID-19) pandemic—underscore the relevance of trauma-related depression as a public health challenge. Clinically, these findings highlight the importance of systematic trauma assessment, early interventions, and integrative strategies encompassing biological, psychological, and social dimensions to mitigate the burden of trauma-related depression.