The Cost of Treating Substance Abuse Patients With and Without Comorbid Psychiatric Disorders

OBJECTIVE: Data from a national sample of patients with a primary diagnosis of a substance use disorder were analyzed to examine whether having a comorbid psychiatric diagnosis—a dual diagnosis—was associated with increased costs of health services over a six-year period and whether dually diagnosed patients used particular types of services more frequently. METHODS: A national sample of substance abuse patients being treated in Veterans Affairs (VA) facilities were classified into two groups—those with a dual diagnosis (N=3,069) and those with a single diagnosis of a substance use disorder (N=9,538). The sample was identified from two sources during a two-week period in 1990: outpatients in specialty substance abuse clinics and inpatients discharged with a substance-related diagnosis. Administrative data were used to track VA health care utilization and costs between 1991 and 1996. RESULTS: Dual diagnosis was associated with a significantly increased total cost of care over the six years, which was primarily explained by increased utilization of outpatient psychiatric and substance abuse services. Costs for both groups decreased over time, but they decreased faster among dually diagnosed patients. CONCLUSIONS: Having a comorbid psychiatric diagnosis appears to consistently increase the cost and utilization of services among patients with a primary diagnosis of a substance use disorder. These results are consistent with previous findings for dually diagnosed patients with a primary psychiatric diagnosis. The increased cost may simply reflect the greater severity of illness among dually diagnosed patients, but it may also indicate fragmented and inefficient service delivery.