Familial risk factors required to predict earlier adolescent substance use in youth with externalizing disorders

Externalizing behaviors and family history of substance-use disorders (SUDs) are well-established childhood predictors of adolescent and adult substance use/SUDs. These two risk factors frequently co-occur and are often confounded in developmental research. This study aimed to disentangle these risk factors and determine to what extent familial-SUD history enhances risk for substance-use/SUD development in youth with externalizing disorders.

SUD risk status of substance-naïve youth (n = 212), aged 11-12 years at baseline, was categorized as high-risk (HR; externalizing disorders and family history of SUDs), psychiatric comparison (PC; externalizing disorders only), or typically developing comparison (TDC). Youth completed a baseline assessment battery and were assessed longitudinally for substance use at 6-month intervals through 18 years of age. Group estimates (HR, PC, TDC) of hazard ratios for substance-use initiation, problematic use, and risky use were estimated using Cox regression models.

HR youth-initiated substance use earlier than both PC youth (adjusted hazard ratio; aHR = 2.31, CI = [1.39, 3.83]) and TDC youth (aHR = 2.68, CI = [1.38, 5.19]). HR youth also transitioned more rapidly than PC/TDC youth to problematic substance use (aHR's 2.16/2.32, CI's [1.19-3.91, 1.05-5.11]) and to risky substance use (aHR's 2.50/2.56, CI's 1.34, 4.59/1.15, 5.67). PC and TDC youth did not differ in substance-use trajectories.

Although there is considerable support for an externalizing behavioral phenotype in youth as a driver toward adolescent substance use, this predictive association was found to manifest only in the context of familial-SUD history. Familial SUD status may warrant particular consideration in the identification of and intervention with youth at risk for SUDs. (PsycInfo Database Record (c) 2026 APA, all rights reserved).