Sample size analysis for future trials
Depression, Anxiety, WL
BADS Cohen’s At Time 2, BADS effect size for AP vs AE was 0.48 (95% CI =  − 0.12 to 1.09) and 0.79 (95% CI 0.08 to 1.50) against WL. The effect size for AE versus WL was 0.31 (95% CI =  − 0.40 to 1.02).At Time 2, HADS-Depression effect sizes for AP versus AE were 0.18 (95% CI =  − 0.42 to 0.79) and − 1.63 (95% CI − 2.36 to − 0.89) against WL. The effect size for AE versus WL was − 1.82 (95% CI =  − 2.56 to − 1.07).Power analyses were conducted using raw BADS and HADS-D estimates, and a range of estimates (range 0.30 to 1.00, based on the Oates et al. [Sample size calculations based on effect size estimates using trial data on the BADS and HADS-D, as well as a range of possible effect size estimates. Estimates do not include expected attrition. Power analyses were conducted based on the primary two-group comparison of interest. An alpha of 0.05 and a beta of 0.80 were used. BADS = Behavioural Activation for Depression Scale; HADS-D = Hospital Anxiety and Depression Scale-Depression