Independent predictors of mortality in adolescents ascertained for conduct disorder and substance use problems, their siblings and community controls.

BACKGROUND AND AIMS: Adolescents with conduct and substance use problems are at increased risk for premature mortality, but the extent to which these risk factors reflect family- or individual-level differences and account for shared or unique variance is unknown. This study examined common and independent contributions to mortality hazard in adolescents ascertained for conduct disorder (CD) and substance use disorder (SUD), their siblings and community controls, hypothesizing that individual differences in CD and SUD severity would explain unique variation in mortality risk beyond that due to clinical/control status and demographic factors. DESIGN: Mortality analysis in a prospective study (Genetics of Antisocial Drug Dependence Study) that began in 1993. SETTING: Multi-site sample recruited in San Diego, California and Denver, Colorado, USA. PARTICIPANTS: A total of 1463 clinical probands were recruited through the juvenile correctional system, court-mandated substance abuse treatment programs and correctional schools, along with 1399 of their siblings, and 904 controls. MEASUREMENTS: Mortality and cause-of-death were assessed via National Death Index search (released October, 2017). FINDINGS: There were 104 deaths documented among 3766 (1168 female) adolescents and young adults (average age 16.79 years at assessment, 32.69 years at death/censoring). Mortality hazard for clinical probands and their siblings was 4.99 times greater than that of controls (95% confidence interval = 2.40-10.40; P < 0.001). After accounting for demographic characteristics, site, clinical status, familial dependence and shared contributions of CD and SUD, CD independently predicted mortality hazard, whereas SUD severity did not. CONCLUSIONS: In the United States, youth with conduct and substance use disorders and their siblings face far greater risk of premature death than demographically similar community controls. In contrast to substance use disorder severity, conduct disorder is a robust predictor of unique variance in all-cause mortality hazard beyond other risk factors.