Persons with dual diagnoses of substance abuse and major mental illness: Their excess costs of psychiatric care

Objectives. This study examined the costs of psychiatric treatment for seriously mentally ill people with comorbid substance abuse as compared with mentally ill people not abusing substances. Methods. Three different sources of data were used to construct client-level files to compare the patterns of care and expenditures of 16395 psychiatrically disabled Medicaid beneficiaries with and without substance abuse: Massachusetts Medicaid paid claims; Department of Mental Health state hospital inpatient record files; and community support service client tracking files. Results. Psychiatrically disabled substance abusers had psychiatric treatment costs that were almost 60% higher than those of nonabusers. Most of the cost difference was the result of more acute psychiatric inpatient treatment. Conclusions. Although the public health and financial costs of high rates of comorbidity are obvious, the solutions to these problems are not. Numerous bureaucratic and social obstacles must be overcome before programs for those with dual diagnoses can be tested for clinical effectiveness.