Delineating mechanisms of change in child and adolescent therapy: methodological issues and research recommendations


Alan E. Kazdin, Child Study Center, Yale University School of Medicine, P.O. Box 207900, New Haven, Connecticut, USA 06520-7900; Tel: (203) 785-5759; Fax: (203) 785-7402; Email:


Background: Mechanisms of therapeutic change are rarely studied in child and adolescent therapy. Our central thesis is that the study of mechanisms of treatment is an excellent investment for improving clinical practice and patient care. Indeed, extending treatment trials to clinical settings, without complementary research that studies why and how treatment works, could have great limitations.

Method: In this article, we discuss the importance of studying mechanisms, the logical and methodological requirements, and why almost no studies to date provide evidence for why or how treatment works. Standard statistical practices (tests of mediation) and designs (randomized controlled clinical trials) contribute greatly to outcome research but have little to say about mechanisms given the way they are commonly used.

Conclusions: The article ends with recommendations to guide research on mechanisms of therapeutic change.