General and Specific Predictors of Comorbid Substance Use and Internalizing Problems from Adolescence to Age 33.

The current study examines the continuity in comorbidity between substance use and internalizing mental health problems from adolescence to adulthood and investigates the general and specific predictors of comorbidity across development. Participants were drawn from the Seattle Social Development Project (N = 808), a gender-balanced, ethnically diverse longitudinal panel. Structural equation modeling was used to examine risk factors for comorbid substance use and internalizing problems in family and peer social environments; substance use- and mental health-specific social environments (family tobacco, alcohol, and marijuana use; family history of depression); and individual risk factors (behavioral disinhibition). Latent factors were created for comorbid substance use and mental health problems at ages 13-14 and comorbidity of substance abuse and dependence symptoms and mental health disorder symptoms at ages 30-33 and included indicators of anxiety, depression, alcohol, tobacco, and marijuana problems. Comorbid problems in adolescence predicted later comorbidity of disorders in adulthood. In addition, family tobacco environment and behavioral disinhibition predicted adolescent comorbidity, while family history of depression was associated with adult comorbidity. Finally, family and peer substance use in adolescence predicted substance use (alcohol, tobacco, and marijuana) both in adolescence and adulthood. The pattern of results suggests that comorbidity in adolescence continues into adulthood and is predicted by both general and behavior-specific environmental experiences during adolescence. Findings clarify the etiology of comorbid internalizing and substance use problems and suggest potential preventive intervention targets in adolescence to curb the development of comorbidity in adulthood.