Is More Treatment Truly Better? A Meta-Analysis of the Dose-Response Effect of Individual Psychotherapy for Treatment of Generalized Anxiety Disorder in Adults.

In the current preregistered meta-analysis, we examined the relation between indicators of treatment amount and effectiveness of individual psychotherapy for generalized anxiety disorder (GAD). We synthesized within-subjects effects from existing randomized controlled trials of individual psychotherapy for adults with GAD (k = 41 studies; n = 1,607 participants). Using random-effects meta-regression, we found that duration of therapy and number of sessions were unrelated to treatment effectiveness. Studies with sessions lasting longer than 60 minutes produced larger effects than sessions shorter than 60 minutes (b = 0.62, 95% confidence interval [CI] [0.21, 1.05]). We also found a trivial relation between therapist contact time and treatment effect (b = 0.02, 95% CI [-0.01, 0.06]). These effects varied based on moderating variables. Our results highlight that more time spent in each session may yield larger treatment effects. Future research should aim to examine different "doses" of psychotherapy in efforts to optimize patient outcomes.