|| Checking for direct PDF access through Ovid
Considerable heterogeneity in patterns of addiction and treatment career histories was observed among the 10,010 clients participating in the Drug Abuse Treatment Outcome Study (DATOS). For half of the clients, DATOS was their first treatment episode; for the other half, their mean number of prior treatment episodes was 3.5. Type of treatment and cumulative length of treatment exposure reflected the interaction of clients' drug use patterns and the historical availability of different treatment approaches. Regression analyses showed that a higher level of prior treatment use was associated with more severe addiction career characteristics, injection drug use, and criminal activities. Effective and cost-effective approaches to treatment need to include more strategic interventions that consider clients' diverse treatment histories.