Drug and Alcohol Dependence 57 (1999) 137–150 Prior treatment experience related to process and outcomes in DATOS Yih-Ing Hser a, *, Christine E. Grella a , Shih-Chao Hsieh a , M. Douglas Anglin a , Barry S. Brown b a UCLA Drug Abuse Research Center, Neuropsychiatric Institute, 1640 S. Sepuleda Bld, Suite 200, Uniersity of California, Los Angeles, CA 90025, USA b Uniersity of North Carolina at Wilmington, Wilmington, NC, USA Accepted 13 April 1999 Abstract Using data collected from cocaine-abusing patients who participated in the Drug Abuse Treatment Outcome Studies (DATOS), we contrasted patients in treatment for the first time and patients having extensive histories of prior treatment to identify factors associated with better outcomes in each group. Compared with first-timers, treatment-experienced patients had less favorable post-treatment outcomes. Indicators of early engagement in DATOS treatment predicted post-treatment abstinence for both groups. Importantly, the interaction of treatment history and several process measures affected post-treatment abstinence. For example, individual counseling and program compliance had greater impacts on abstinence among treatment repeaters in outpatient drug-free programs than for first-timers. Social support and environmental context were significantly related to abstinence. These findings confirm the importance of considering treatment process and aftercare in developing and implementing strategies to optimize treatment for patients with different treatment histories. © 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Drug treatment history; Treatment process; Treatment outcome; Social support; Environmental context; Cocaine use www.elsevier.com/locate/drugalcdep 1. Introduction Increasing the effectiveness of treatment for individu- als with distinctive histories of drug abuse and prior treatment would improve overall patient outcomes, re- duce the likelihood of repeat treatment episodes, and curtail the social costs associated with relapse. Data from the recent national Drug Abuse Treatment Out- come Studies (DATOS) (Anglin et al. 1997) have shown that approximately one-half of patients entered treat- ment for the first time, while the other half were treatment-repeaters, many of whom had multiple prior treatment admissions and lengthy periods of treatment involvement. Patients with prior treatment histories were characterized by more severe levels of drug use, criminality, and use of drugs by injection. Given the high proportion of repeaters and the associated high social and personal costs of untreated drug dependence, it is important to determine if and how differences in program services may be optimally effective with each type of patient. In a prior study of treatment first-timers and re- peaters in DATOS long-term residential programs, we found that treatment repeaters were, in general, more difficult to treat; however, their likelihood of achieving sustained abstinence was similar to first-timers if they were retained in treatment for a sufficient period of time (Hser et al., 1999b). This initial study had catego- rized prior treatment history as either the presence or absence of any treatment. In light of the considerable heterogeneity in treatment histories indicated by the wide range in the number of prior treatment episodes reported by repeaters, further exploration of how prior treatment experience is related to treatment process and outcomes in DATOS is warranted. Of particular con- cern to society are those drug users who have been in and out of treatment programs multiple times, perhaps * Corresponding author. E-mail address: yhser@ucla.edu (Y.-I. Hser) 0376-8716/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved. PII:S0376-8716(99)00081-2