Bridging Disciplinary Boundaries (January 11 - 14, 2007)

PURPOSE: Despite the demonstrated benefits of providing on-site medical and psychosocial services to methadone patients, methadone maintenance treatment programs (MMTPs) are increasingly relying on referral to off-site service providers for patients with co-occurring needs beyond addiction. However, the question of whether receipt of off-site, supplemental services improves drug treatment outcomes (i.e., increases abstinence from illicit drug use) among methadone patients has not been answered. Using data from a longitudinal panel study of male MMTP clients, this study aims to generate causally valid estimates to test hypotheses regarding the effects of utilization of off-site, supplemental services on illicit drug use. METHODS: Randomly selected men attending MMTPs in New York City participated in a longitudinal panel study where participants (N=356) was interviewed 3 times, with 6 months between each interview. Participants provided self-reported data on illicit drug use, sociodemographics (e.g., age, race/ethnicity, health insurance); symptoms of psychological distress using the Brief Symptom Inventory; number of stressful life events (e.g., being mugged, homeless periods, life-threatening illness) using the Life Events Questionnaire; and use of supplemental services (e.g., primary/emergency healthcare, mental health, social work) using the Treatment Services Review. The latter two instruments were modified and tailored for urban, poverty-stricken communities and assessed events/behaviors over the preceding 6 months. Since this observational study did not employ random assignment, to strengthen causal validity of effect estimates, propensity score matching was employed to address potential self-selection bias between service users and non-service users. After propensity score matching, multivariate logistic regression models were used to estimate the impact of off-site, supplemental service utilization on illicit drug use during the time period subsequent to service utilization. RESULTS: The mean age of participants was 44 years, with 38% identifying as African American and 45% as Latino. At the first assessment, the prevalence of any illicit drug use during the prior 6 months was 78%; 51% of the sample reported using heroin, 38% used marijuana, and 33% used cocaine. About 30% of the participants utilized off-site, supplemental services, with service users reporting significantly more years of education, number of stressful life events, and levels of psychological distress compared to those who did not utilize off-site, supplemental services. After propensity score matching, logistic regression analyses indicate that utilization of off-site supplemental services has significant beneficial effects in increasing the likelihood of abstinence from heroin (OR=3.6, 95%CI=1.5-9.1), cocaine (OR=4.8, 95%CI=1.9-12.5), and any illicit drug use (OR=3.5, 95%CI=1.3-9.1) during the subsequent 6 months. CONCLUSIONS: These findings indicate that receipt of off-site, medical and/or psychosocial services may represent a key ingredient to enhancing the efficacy of methadone treatment in reducing illicit drug use, and that referral to off-site service providers is an efficacious option if provision of such services within the MMTP is not possible. Additional implications for both social work research and practice in drug treatment settings will be discussed.