ABSTRACT
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.
