Abstract
Collective traumas, such as war, genocide, natural disasters, and systemic oppression, have profound and lasting effects, not only on survivors but also on their descendants. Understanding how these traumas are transmitted across generations is essential to inform effective interventions and policy responses. This systematic review aimed to synthesize quantitative evidence on the physiological and psychological outcomes observed in second-generation descendants of individuals exposed to collective trauma. We included English-language, peer-reviewed quantitative studies published between 1997 and 2022 that investigated intergenerational trauma among second-generation descendants of survivors of collective trauma. Exclusion criteria included qualitative studies, and those that involved third-generation descendants. We conducted a comprehensive search across six databases: PsycINFO, PsycARTICLES, MEDLINE, Web of Science Core Collection, Embase, and PubMed. The final search was completed in December 2022. Search terms included keywords such as "intergenerational trauma," "transgenerational trauma," "collective trauma," and "historical trauma." Two independent reviewers screened titles and abstracts, followed by full-text assessments for eligibility. Discrepancies were resolved through discussion. Study quality was evaluated using the Critical Appraisal Skills Programme (CASP) checklist. Each study was assessed independently by two reviewers, with disagreements resolved by consensus. A narrative synthesis was conducted. Out of 3,904 records identified, 18 studies met the inclusion criteria. The findings revealed that physiological changes in stress regulation and brain structure suggest biological embedding of trauma across generations. Socially, intergenerational trauma shaped relationships and identity, often fostering mistrust and emotional restraint. Psychologically, descendants showed elevated distress and trauma symptoms, with parental PTSD as a key predictor. The overall quality of evidence was limited by small sample sizes, cross-sectional designs, reliance on self-reported measures, and inadequate control for confounding factors. More longitudinal and methodologically rigorous studies are needed to better understand the pathways of trauma transmission and inform prevention and intervention strategies. This review was registered with PROSPERO (CRD42023433181).