General and Specific Predictors of Comorbid Mental Health and Substance Use Problems from Adolescence to Age 33

Background

The occurrence of comorbid substance use and mental health problems is a critical issue in clinical social work practice and for public health because this form of comorbidity is associated with worse clinical outcomes, and more severe impairment (Merikangas et al., 1998; Kessler et al., 2005).  Little is known about the development of comorbidity over the life course, including to what degree social environmental or individual risk and protective factors predict substance use and mental health problems uniquely or their comorbidity generally. Little is also known about how these effects differ during adolescence vs. adulthood.  This analysis examines the unique (e.g., family smoking) and general (e.g., family functioning) predictors of adolescent and adult comorbidity in mental health and substance use problems.

Methods

Participants are from the Seattle Social Development Project, a gender balanced, ethnically diverse (53% non-white) longitudinal panel of 808, recruited from elementary schools serving high crime neighborhoods in 1985 (age 10) and followed into adulthood. Structural equation modeling was used to examine general (family functioning, peer social environment) and specific (family tobacco use, family alcohol use, family marijuana use, family history of depression) social environmental (ages 10-12) and individual risk factors (behavioral disinhibition). Comorbidity was modeled as a latent factor at age 13-14 and again at age 30-33. Indicators at age 13-14 included teacher reported depression and anxiety behavior, self-reported alcohol tobacco and marijuana use, and indicators for comorbidity at age 30-33 included DSM-IV symptom counts of generalized anxiety and major depressive disorders, and symptoms of alcohol, tobacco or marijuana abuse or dependence.

Results

There was continuity in comorbidity between mental health and substance use problems from age 13-14 to age 30-33.  General risk factors of poor family functioning and behavioral disinhibition predicted adolescent, but not adult comorbidity. The influence of family history of depression, predicted general comorbidity and adult anxiety and depression at age 30-33.  Similarly, childhood family tobacco, marijuana and alcohol use predicted tobacco, marijuana and alcohol use (respectively) in adulthood, but not adolescence.  Childhood peer substance use specifically predicts use of all three substances in adolescence and adulthood.  Behavioral disinhibition is also an important individual risk factor for comorbid problems in adolescence, but by adulthood, behaviorally disinhibition relates to use of all three substances. 

Conclusions

The pattern of results suggests that although there was continuity in comorbidity from adolescence to adulthood, different risk factors predicted both comorbidity and unique problems at different ages. Behavioral disinhibition and family functioning in childhood relate to comorbidity in adolescence, which in turn increases comorbidity in adulthood. Understanding the etiology and development of comorbid mental health and substance use problems can help in preventing and treating comorbid mental health and substance use problems that may not be served by existing interventions that target one without the other.