Medical Morbidity, Mental Illness, and Substance Use Disorders

OBJECTIVE: Previous research on the prevalence of medical disorders among adults with mental illness has been inconclusive. In general, studies have found higher rates among persons with mental illness, but these studies did not account for comorbid substance use disorders. The authors examined whether certain medical disorders are more prevalent among adults with severe mental illness and whether a comorbid substance use disorder increases prevalence beyond the effect of severe mental illness alone. METHODS: Administrative data from the Massachusetts Division of Medical Assistance were used in a cross-sectional observational study design. The sample consisted of 26,332 Medicaid beneficiaries 18 to 64 years of age. Of these, 11,185 had been treated for severe mental illness. Twelve-month prevalence rates were computed, and logistic regression was used to estimate the effect of a substance use disorder or another mental illness on the risk of having a medical disorder. RESULTS: Compared with Medicaid beneficiaries who were not treated for severe mental illness, those with severe mental illness had a significantly higher age- and gender-adjusted risk of the medical disorders considered in the study. Those with a comorbid substance use disorder had the highest risk for five of the disorders. CONCLUSIONS: The higher treated prevalence of certain medical disorders among adults with severe mental illness has three implications: substance use disorder is an important risk factor and requires early detection; integration of the treatment of medical disorders and severe mental illness should receive higher priority; and efforts should be made to develop specialized disease self-management techniques.