What is it about?

We comment on a recent meta-analysis of the benefits of Cognitive Behavioral Therapy (CBT) for treating the depression, anger, and anxiety experienced by adults with intellectual disability. A longstanding criticism of meta-analytic studies of psychotherapy outcomes is that they (1) fail to take into account differences in the quality of the studies included in the meta-analysis, (2) aggregates studies that differ in the form of therapy delivered, and (3) do not consider the bias arising from the non-publication of studies failing to find an effect. To their credit, the researchers address the quality issue by assessing the included studies on methodological rigor and risk of bias using standardized rating scales. Furthermore, they analyzed the data in terms of whether the studies employed randomized controlled trials and controlled trials, or uncontrolled trials. The mixing of treatments that were similar but not exactly the same was unavoidable given the small number of relevant studies identified (i.e., only 22), but it can also be viewed as providing evidence for generalizability instead of a weakness. A limitation is that the investigators did not check for the presence of publication bias and, if necessary, adjust their derived effect sizes for this distortion. More than likely, the reported effect sizes are over-estimates. It is argued by us that the potential of meta-analysis will not be realized fully until major improvements occur in the studies that serve as the basis for the meta-analysis. Changes need to occur in journal policies allowing for the publication of replications and well-designed null studies.

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Why is it important?

This article highlights the importance of empirically demonstrating Psychology's commitment to evidence based practice.


We need to honor the leadership of former APA president Donald Campbell who called for empirical evaluations of social service programs, essentially founding the field of program evaluation.

Scott Spreat
Woods Research Institute

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This page is a summary of: Commentary on “Cognitive-behavioral therapy for adults with intellectual disabilities: A meta-analysis” by Graser et al. (2022)., Clinical Psychology Science and Practice, September 2022, American Psychological Association (APA), DOI: 10.1037/cps0000095.
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