Meta-Analysis of Homework Effects in Cognitive and Behavioral Therapy: A Replication and Extension

Kazantzis, Deane, and Ronan (2000) estimated the effect size (ES) for homework's causal effects on outcome, but did not (a) estimate ES for "control" therapy conditions, (b) incorporate data from correlational studies, or (c) test for outliers. The present analysis (46 studies, N = 1,072) replicated and extended Kazantzis and colleagues' review and obtained a pre-posttreatment ES of d = 0.63 for control conditions, and a larger d = 1.08 for therapy conditions with homework. A pooled ES of d = 0.48 favoring homework was obtained when the analysis was restricted to controlled studies contrasting the same therapy. No evidence was found for outlier or publication bias effects. Results supported the conclusion that homework assignments enhance therapy outcomes.