Publication bias and the evaluation of psychotherapy efficacy in reviews of the research literature

Since evaluations of psychotherapy efficacy have become increasingly dependent on reviews of the research literature, which is comprised mainly of published studies, such evaluations are vulnerable to the effects of publication bias. Publication bias is a bias against studies with negative findings, on the part of authors, reviewers, and editors, which can lead to the systematic exclusion of negative findings from the published literature. The result of such an exclusion is the portrayal of the support for a proposition as being stronger than it actually is. An appraisal of measures taken to insure that the support for the proposition of psychotherapyʹs efficacy found in the research literature is not an artifact of publication bias is undertaken. The finding is that those measures, without exception, have not been up to the task. The inherent difficulty of reaching conclusions on the basis of a literature review is discussed.