Multi-Morbidity, Serious Mental Illness, and Substance Use Disorders: An Analysis of Factors Related to Medical Complexity

Purpose: Individuals with serious mental illnesses (SMI) and substance use disorders (SUD) are at increased risk for multi-morbid chronic health conditions such as diabetes and hypertension. Research has also shown associations among multi-morbidity and greater medical and treatment complexity, higher costs and higher mortality rates. To date, however, the associations among SMI, SUD and chronic health conditions have been studied in the context of single conditions. Hence, the overall magnitude of the risk for multi-morbidity and which medical conditions, if any, tend to most commonly cluster among those with SMI/SUD have not been identified. Better understanding the nature of these relationships could potentially improve screening, diagnosis, and care coordination for medically complex individuals with multi-morbid conditions. Methods: We analyzed data from the 2008 National Household Survey on Drug Use and Health for participants 18 years of age or older (n=37,145). The dependent variable was the total number of chronic health conditions assessed through sixteen questions and collapsed into four categories to represent increasing medical complexity: 0, 1, 2, and 3 or more conditions. Predictors included a dichotomous indicator of SMI as assessed by the K6 scale, and any past-year alcohol or other SUD. The model included demographic covariates representing: gender, race/ethnicity, age, employment, and health insurance status (Medicaid/Medicare, Private). Interactions between SUD/SMI and for SMI/gender were also explored. Data analysis used a partial proportional odds model after preliminary diagnostics indicated not all predictors met the assumption of proportional odds. Post-hoc analyses examined which specific health conditions were associated with increased multi-morbidity among those with SMI/SUD. Results: After adjusting for covariate effects, both SMI and SUD were significantly but non-linearly related to multi-morbidity. Respondents with an SMI were 66% more likely to experience at least one chronic health condition than those with no SMI. As medical conditions accumulated, the effect of SMI increased. Respondents with SMI were 89% more likely to report two or more medical conditions than those without and 147% more likely to report 3+ conditions. A different pattern emerged for those reporting an SUD. Respondents with an SUD were no more likely to report one or two medical conditions than those with no SUD but were 40% more likely to report three or more medical conditions. The interaction terms were not-significant. Conditions such as bronchitis, pneumonia, and heart disease, diabetes, and strokes were especially common among participants in highest multi-morbidity category. Implications: These findings suggest a need for greater collaboration between social workers and medical health professionals and increased specialized training on the intersections of SMI, SUD, and chronic health conditions for professionals in either discipline. They also suggest the need for greater linkages between delivery systems and highlight the importance of reaching out specifically to SMI/SUD clients who are often hard to reach. To achieve these collaborative goals, it is necessary to develop targeted interventions in both health and social work settings that focus on the health needs of those with an SMI or SUD and the health challenges that result.