Objective: The authors reviewed studies of Medicaid spending on mental health and substance abuse services. Methods: Studies were identified through a search of MEDLINE and bibliographies of known articles on mental health and substance abuse spending and by searching Web sites of or contacting key government and private organizations. Of 448 studies identified, the 14 that included Medicaid expenditure percentages for 1984 or later were compared. Results and conclusions: The most comprehensive studies of such spending suggest that between 9.3 and 13 percent of all Medicaid dollars are spent on behavioral health services. The most comprehensive estimates came from claims-based studies or studies based on the National Health Accounts. Studies based on provider or consumer surveys missed large portions of Medicaid spending. Policy makers need to ensure that they use the most accurate data to track mental health and substance abuse spending, an important part of total Medicaid expenditures.
