We included two variables from the initial treatment episode: (1) treatment type: day hospital versus traditional outpatient, and (2) the length of time in treatment without dropping out for 7 days during the 8-week rehabilitation phase, or dropping out for 30 days during the 10-month aftercare phase (Mertens and Weisner, 2000). We also measured treatment readmissions following the initial episode. We calculated length of time in treatment and readmissions from the health plan’s automated administrative data system. Readmission was defined as having at least three visits (and no more than 30 days between visits) to a chemical dependency program between 1 and 4 years after intake (Mertens et al., 2005). We do not equate readmissions with relapse; for example, readmissions can also measure visits of brief support to maintain abstinence.
