Introduction to the special issue: treatment process in DATOS

Several important findings from the drug abuse treatment outcome studies (D ATOS) are presented in this issue of drug and alcohol dependence. These stu dies focus on the drug abuse treatment process in areas of engagement in tr eatment and participation in program activities, the effect of the patient' s age and treatment history in predicting treatment retention and outcomes, and the impact of prior treatment experience on the level of treatment eng agement and subsequent outcomes. A cost-benefit model for drug abuse treatm ent is developed. Significant contributions are made in the development of a comprehensive model of the treatment process, including the relationship of patient attributes, program factors, and outcomes. Findings on retention from the United Kingdom's national treatment outcome research study (NTORS ), a study similar in design to DATOS, also are presented. (C) 1999 Elsevie r Science Ireland Ltd.