Sudden gains in routine care cognitive behavioral therapy for depression: A replication with extensions.

BACKGROUND: Over the last decade, a substantial amount of findings have been reported on the association between sudden gains (large symptom improvements in a between-session interval) and treatment outcome. Accurate replications of previous findings are needed to tackle inconsistencies and to shed light on the clinical implications of sudden gains. This study investigates whether similar effects of sudden gains can be expected under routine care conditions, when the patients are comparable to those examined in the original study by Tang and DeRubeis (1999).

METHOD: Using propensity score matching (PSM), 462 patients treated with cognitive behavioral therapy (CBT) under routine conditions were matched stepwise to patients of the original study on sudden gains, a randomized controlled CBT trial (RCT).

RESULTS: After the application of PSM, the effects of sudden gains on treatment outcome were similar to those found by Tang and DeRubeis (1999). The closer the match between the RCT and the naturalistic sample, the more similar the association between sudden gains and treatment outcome.

CONCLUSION: Sudden gains seem to have a significant impact on recovery rates, even in treatments under routine care. Results suggest that one important aspect of replication success is to control for confounding baseline covariates.