Early Adverse Experiences and the Likelihood of Substance Use Disorders and Non-Fatal Overdose in Clinical and...

Early adverse experiences may increase the likelihood of substance use disorders/addictions (SUD) and overdose, but estimates vary across settings. This review synthesised observational evidence on early adverse experiences and disorder-level SUD outcomes and/or non-fatal overdose. PubMed, Scopus, Web of Science, ScienceDirect, SpringerLink, and Taylor & Francis were searched up until 1 December 2025. Eligible observational studies sampled psychiatric treatment or community populations, measured early adverse experiences, and reported associations with disorder-level SUD/addiction or non-fatal overdose. Risk of bias was assessed using Joanna Briggs Institute (JBI) tools. A random-effects meta-analysis pooled commensurate overdose estimates; the remaining evidence was synthesised narratively. Nine studies were included (n = 67,228 participants; one cohort did not report an analytic sample size). SUD associations were consistently positive (adjusted odds ratio (OR) range 1.71-4.30) but were not pooled due to heterogeneity in exposure and outcome definitions. Three studies (721 participants) contributed to the overdose meta-analysis; a higher adverse childhood experience (ACE) score was associated with higher odds of non-fatal overdose (pooled OR 1.16 per +1 ACE, 95% confidence interval (CI) 1.06-1.28; I² = 28.4%). A Hartung-Knapp sensitivity analysis yielded OR 1.16 (0.95-1.41). Risk of bias was mostly moderate, commonly driven by self-reported outcomes and residual confounding. Early adverse experiences were associated with higher odds of SUD and non-fatal overdose across settings. Limitations include observational designs, variable measurement, and sparse poolable overdose evidence; future studies should distinguish fatal from non-fatal overdose and improve outcome harmonisation.