OBJECTIVES: To examine the association between childhood trauma and substance use and behavioural addictions in adults, including comorbid mental and physical illness, and to identify mediating and moderating mechanisms.

METHODS: A systematic review was conducted following PRISMA guidelines and registered on PROSPERO. Five databases (PubMed/MEDLINE, EMBASE, PsycINFO, Web of Science, and Cochrane) were searched for English-language studies published between 2006 and 2025, with an updated search in March 2026. Adults with a diagnosed substance use or behavioural addiction disorder, assessed using the Childhood Trauma Questionnaire (CTQ or CTQ-SF), were included. Cross-sectional, cohort, and case-control designs were eligible. Risk of bias was assessed using the Newcastle-Ottawa Scale.

RESULTS: Sixty-seven studies encompassing 44,429 participants were included. Emotional neglect and emotional abuse were the most frequently reported trauma types. Alcohol was the most common addiction. Depression was the predominant mental health comorbidity, present in over half of reporting studies. Three themes emerged: psychological and psychosocial mediators (particularly impulsivity, emotional dysregulation, and negative self-concept); neurobiological correlates including structural, functional, and molecular brain alterations; and gender as a significant moderator, with women demonstrating more severe trauma profiles and stronger associations between trauma and relapse.

CONCLUSIONS: Childhood trauma is consistently associated with addiction across diverse populations and settings. The relationship is substantially mediated by modifiable psychological factors, supporting trauma-informed, gender-responsive approaches in addiction treatment. Routine trauma screening and integrated mental health care are indicated.