The effects of psychological therapies under clinically representative conditions: A meta-analysis

Recently, concern has arisen that meta-analyses overestimate the effects of psychological therapies and that those therapies may not work under clinic ally representative conditions. This mete-analysis of 90 studies found that therapies are effective over a range of clinical representativeness. The p rojected effects of an ideal study of clinically representative therapy are similar to effect sizes in past meta-analyses. Effects increase with large r dose and when outcome measures are specific to treatment. Some clinically representative studies used self-selected treatment clients who were more distressed than available controls, and these quasi-experiments underestima ted therapy effects. This study illustrates the joint use of fixed and rand om effects models, use of pretest effect sizes to study selection bias in q uasi-experiments, and use of regression analysis to project results to an i deal study in the spirit of response surface modeling.