Externalizing Disorders and Substance Use Among Nigerian Adolescents: Prevalence, Comorbidity, and Dose-Response Association.

Objective: To estimate prevalence of externalizing disorders (attention-deficit/hyperactivity disorder, oppositional defiant disorder, and conduct disorder) among Nigerian adolescents and examine associations with substance use disorder (SUD), alcohol use disorder (AUD), and associated factors. Method: A cross-sectional analysis of 9,437 adolescents aged 11 to 17 years from 47 Lagos State public secondary schools was conducted using the Mini International Neuropsychiatric Interview for Children and Adolescents (MINI-Kid) adapted for self-administration within its validated age range. Weighted multivariable logistic regression examined associations adjusting for demographic, family, and school factors. Results: Overall, 15.1% of adolescents met criteria for at least 1 externalizing disorder, with male predominance (17.7% vs 12.4%; odds ratio 1.52, 95% CI 1.35-1.71). Comorbidity was common, with 43.7% meeting criteria for 2 or more diagnoses. A graded dose-response association was observed: each additional co-occurring diagnosis was associated with a 2.84-fold increase in SUD odds (95% CI 2.48-3.25). Adolescents meeting all 3 disorder criteria showed SUD prevalence of 18.8% (adjusted odds ratio [AOR] 9.87, 95% CI 5.84-16.68) and AUD prevalence of 23.2% (AOR 6.73, 95% CI 3.91-11.59) compared with adolescents with no externalizing disorder. Class repetition (AOR 2.26, 95% CI 2.00-2.55), maternal drinking (AOR 1.69, 95% CI 1.15-2.48), and witnessing domestic violence (AOR 1.64, 95% CI 1.35-1.99) were most strongly associated with externalizing disorders. Conclusion: Externalizing disorders are common among Nigerian adolescents and are strongly associated with substance use and functional impairment. The observed dose-response pattern is consistent with developmental cascade models; longitudinal research is needed to establish sequential disorder progression. School-based screening and integrated behavioral and academic interventions may reduce associated substance use burden. Diversity & Inclusion Statement: We worked to ensure sex and gender balance in the recruitment of human participants. We worked to ensure race, ethnic, and/or other types of diversity in the recruitment of human participants. We worked to ensure that the study questionnaires were prepared in an inclusive way. We actively worked to promote sex and gender balance in our author group. While citing references scientifically relevant for this work, we also actively worked to promote sex and gender balance in our reference list.