The study, published in the latest issue of Health Affairs, shows that completion disparities among racial groups are likely related to differences in socioeconomic status and, in particular, greater unemployment and housing instability for black and Hispanic patients. The researchers suggest that funding for integrated services and increased Medicaid coverage under the Affordable Care Act (ACA) could help to improve access to treatment programs for minorities.

"Our findings show troubling racial disparities in the completion of alcohol and drug abuse programs, and they point specifically to socioeconomic barriers that make it difficult for minority groups to access and sustain treatment," said Brendan Saloner, PhD, a health services researcher at the Perelman School of Medicine at the University of Pennsylvania, and a Robert Wood Johnson Foundation Health and Society Scholar at Penn. "For example, in both alcohol and drug treatment groups, black and Hispanic patients were more likely than white patients to be homeless. But, disparities among the groups were found to be lower in residential treatment settings, indicating that access to residential treatment could be particularly valuable for these patients."

After analyzing data from more than one million discharges from treatment programs across the country, researchers found significant disparities between white patients and most minority groups in completion of treatment programs. According to researchers, the statistical differences roughly translate to 13,000 fewer completed episodes of drug treatment for black patients and 8,000 fewer for Hispanic patients, compared to white patients. Other minority groups, including Native Americans, also showed lower completion rates than white patients. Only Asian American patients fared better than white patients for both drug and alcohol treatment completion.

According to the data -- from the Substance Abuse and Mental Health Services Administration (SAMHSA)'s 2007 Treatment Episode Data Set -- reasons for incomplete treatment included leaving against professional advice, incarceration, or having treatment terminated by the facility because of noncompliance. Saloner says socioeconomic barriers could operate in several ways to hinder treatment completion.

"Patients living in poverty may be more likely to receive treatment in an environment with high social distress, weak social support, or few economic opportunities," he said, adding that these external factors could undermine individual engagement with treatment or create competing demands, leading to higher dropout rates from treatment. "Unfortunately, it's possible that funding for treatment programs may be limited in the future as states and the federal government look for ways to trim spending on public programs. However, in the long run, these reductions in spending on treatment programs may lead to increased spending for corrections and emergency department admissions."

The researchers suggest that steps to broaden Medicaid funding in the Affordable Care Act could dramatically improve access. To be particularly effective, the policies should focus on points in the treatment process where vulnerable groups -- particularly minorities -- are likely to drop out of treatment. Broadened access to supported housing and vocational training could be two cost-effective ways of improving overall substance-addiction treatment results and reducing treatment outcome disparities, in addition to addressing significant public policy problems.

Saloner's co-investigator on the study was Benjamin Lê Cook, PhD, assistant professor in the Department of Psychiatry at Harvard Medical School.

Funding for the study was provided by the National Institute on Minority Health and Health Disparities (P60MD002262), and the National Institute of Mental Health (R01MH091042).