Enhancing substance abuse treatment evaluations: examining mediators and moderators of treatment effects.

This article considers ways in which the basic, comparative approach to evaluating treatment for substance abuse is sometimes enhanced. The general strategy has been to make treatment evaluation projects explanatory by embedding them in a theoretical framework. Using either a theory of the treatment process or of patient-treatment matching guide, the typical approaches for enhancing comparative treatment evaluations are to identify either mediators or moderators of treatment effects. In addition to addressing the basic question of "Does the treatment work or not work?" one can also ask in more explanatory evaluations: "How or why does the treatment work or not work?" and/or "For whom do treatments work or not work?" Variations of these questions that can be addressed in treatment process and patient-treatment interaction effect analyses are discussed. Particular attention is given to explaining (identifying mediators of) patient-treatment interaction effects. Some advantages of making treatment evaluations more explanatory are discussed.