Contemporaneous relationship between substance abuse treatment and poly-substance use: evidence from the Persistent Effect of Treatment Studies.

Data from the Persistent Effect of Treatment Studies (PETS) are used to explore the relationship between duration of substance use treatment and simultaneous poly-substance using behaviors. Studying such contemporaneous relationships is especially important given the chronic nature of the substance-using population (McLellan, 2002) in the PETS study. Data were collected at intake to treatment programs and follow-up interviews were performed periodically at treatment program sites. One of the features of the analysis was the development of a poly-substance scale to measure multiple substance use. Multilevel models were implemented to examine the relationship between three levels of care (i.e., intensive outpatient, outpatient, and residential) and simultaneous poly-substance use. Contemporaneous effects of treatment were obtained such that higher duration of treatment was associated with drops in substance-using behaviors. This result supports the need for sustaining treatment for a population of chronic substance abusers.