Genetic and Environmental Risk Factors for Intermittent Explosive Disorder, ADHD and Conduct Disorder: Shared and...

This systematic review examines the shared and unique risk factors for intermittent explosive disorder (IED), attention-deficit/hyperactivity disorder (ADHD) and conduct disorder (CD), aiming to provide a comprehensive understanding of their etiological pathways and inform future intervention strategies.

We conducted a comprehensive search across seven databases (Web of Science, APA PsycINFO, MEDLINE, PubMed, Cochrane, CENTRAL and Embase) for studies examining risk factors for IED, ADHD and CD. A total of 44 studies were included, focusing on genetic, environmental and psychosocial factors. We employed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines for study selection and quality assessment.

Forty-four studies were included. We identified 15 cross-disorder risk factors. Of these, nine domains had evidence across all three disorders. The remaining six domains showed a more restricted pattern (present for ADHD and/or CD, but not yet studied or not reported for IED): maternal smoking during pregnancy, maternal alcohol use during pregnancy, low birth weight/other perinatal risks, parental psychopathology/maternal mental health, MAOA/COMT genetic variants and parenting stress/school-related disadvantage that has not been tested for IED.

Our findings emphasise the importance of shared environmental and biological factors across these disorders, with implications for integrated intervention strategies. The review highlights gaps in research and calls for more targeted studies that incorporate gender, developmental stage and family dynamics.