Abstract
Ost (2008) recently compared the methodological rigor of studies of acceptance and commitment therapy (ACT) and traditional cognitive behavior therapy (CBT). He concluded that the ACT studies had more methodological deficiencies, and thus the treatment did not qualify as an "empirically supported treatment." Although Ost noted several important limitations that should be carefully considered when evaluating early ACT research, his attempt to devise an empirical matching strategy by creating a comparison sample of CBT studies to bolster his conclusions was itself problematic. The samples were clearly mismatched in terms of the populations being treated, leading to differences in study design and methodology. Furthermore, reanalysis showed clear differences in grant support favoring CBT compared with ACT studies that were not reported in the original article. Given the actual mismatch between the samples, Ost's methodological ratings are difficult to interpret and provide little useful information beyond what could already be gathered by a qualitative review of ACT study limitations. Such limitations are characteristic of the earlier randomized controlled trials of any emerging psychotherapeutic approach.