COMMENTARY

The paper by Chen and her colleagues addresses an important and topical question.Can cognitive-behavioral therapy (CBT) for bulimia nervosa be delivered in amore economical manner without a major decrement in therapeutic effectiveness andwithout harming those treated? The format chosen was group CBT (GCBT) comparedto individual CBT (ICBT) in a randomized controlled trial. This happens to be aquestion dear to my heart, because the first studies of CBT from Stanford were in agroup format (Kirkley, Schnoider, Agras, & Bachman, 1985; Schnoider & Agras 1985)and were reasonably effective. Thereafter, a group comparison was added to severalproposed studies of ICBT, but although the grants were funded, the group conditionwas always excised by the reviewers. It is quite remarkable that 20-years later this is thefirst time that this important question has been addressed in a well-designed studywith many methodological refinements. Hence, it was with great interest that I read thispaper.

What were the results of this interesting study? As usual it depends on one’s perspec-tive. From a statistical viewpoint there were essentially no differences between the twotreatments. The treatment effects appear substantial and, as the authors note, are com-parable to other studies of ICBT reported in the literature. Hence, by my calculation therewas a 76% decline in objective binge eating, and a 79% decline in vomiting from pre- toposttreatment for ICBT and a 62% and 41% decline for GCBT, neither comparison wasstatistically significant. Many of the measures are close to, or lower than the criterionscore calculated by the authors and are again largely comparable between groups. On acomparison of abstinence, however, ICBT was superior to GCBT at the end of treatment,but not at follow-up. Dropout rates were equivalent between the groups and at 27% arecomparable to the existing literature on ICBT. From this perspective it appears that GCBTis as effective a treatment as ICBT, and because it is less costly than ICBT, it might wellform the first treatment is a stepped-care approach. Indeed one might argue that GCBTcould be recommended to patients as a first line less expensive approach to the treatmentof bulimia nervosa.

However, a closer look from a more clinical perspective raises some doubts about theseconclusions. If abstinence from binge eating and vomiting is regarded as the mostrelevant criterion of clinical improvement then for the end of treatment intent-to-treatanalysis 20.0% of ICBT participants were abstinent compared with 0% for GCBT, astatistically significant difference as the authors note. At follow-up, however, thegroups were not significantly different with 16.7% of ICBT participants and 3.3% ofGCBT participants abstinent. It should be noted that abstinence from binge eatingincluded both subjective and objective binges. This is a very conservative estimateand may reduce the percentage abstinent somewhat. How troubling are these numbers?Given the fact that the assessment and criteria used for abstinence are state-of-the-art,the results for GCBT cannot be compared with those from earlier studies. However, forICBT the proportion of participants reaching and maintaining abstinence appearscomparable to studies that have used similar assessments and reported intent-to-treatfindings. The findings for GCBT, on the other hand, appear to fall into the range reportedfor wait-list or placebo conditions. However, comparisons across studies are problematicbecause of the possibility of population or other differences between studies.

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Nonetheless, if taken at face value it is hard to recommend a treatment (GCBT) forwhich 96.7% of patients, although improved, will not reach the desired clinical outcome.However, such a treatment might form the first phase of a stepped care program (GCBTfollowed by ICBT if needed) if it could be shown that this package was as, or moreeffective, than ICBT and was less costly. It would be problematic, however, if the dropoutrates from the second step of treatment (ICBT) were similar to those encountered in thefirst phase, and if demoralization over treatment failure occurred then dropout in thesecond phase of treatment might be even greater.

A few methodological points. One problem in the interpretation of this study, as theauthor’s note, is the limited sample size. Power calculations based on the results reportedsuggest that the power varied between 0.1 and 0.75 for the primary outcomes. Hence, theprobability of missing true differences between the treatment groups is quite large. Inaddition, the distributions of binge eating and purging are not normal and the variancesare large and differ between groups. It might have been useful to use a square roottransformation to normalize the data. Finally, I am not sure that adding subjective bingeeating to objective binge eating as an outcome criterion is helpful because the assessmentof subjective binge eating does not appear to be reliable (Rizvi, Peterson, Crow, & Agras,2000).

Taking into account these differing perspectives one must conclude that it is uncertainat this time whether GCBT is in fact equivalent to ICBT. What might the next steps be inresearch along these lines? Taking the literature on GCBT as a whole it would seemworthwhile to conduct a larger scale study with adequate power comparing GCBT andICBT. As the authors note, a third group should probably be added, for example, apsychotherapy without the specific ingredients of CBT. There are, of course, othercontenders for a stepped care study such as therapist-assisted self-help. The advantageof this treatment is that it uses relatively little therapist time per patient and in pre-liminary studies appears to achieve reasonable results. A large-scale study is now inprogress comparing the utility of this treatment as the first phase of a stepped-care study,followed by antidepressant medication and full CBT if needed, compared with full CBTaugmented by antidepressant medication if needed. This study will also consider therelative cost-effectiveness of the two treatment sequences. A stepped-care treatment isonly useful if it reduces the costs of care without reducing the overall effectiveness oftreatment.

REFERENCES

Kirkley, B.G., Schneider, J.A., Agras, W.S., & Bachman, J.A. (1985). Comparison of two group treatments forbulimia. Journal of Consulting & Clinical Psychology, 53, 43–48.

Rizvi, S.L., Peterson, C.B., Crow, S.J., & Agras, W.S. (2000). Test-retest reliability of the eating disorderexamination. International Journal of Eating Disorders, 28, 311–316.

Schneider, J.A., & Agras, W.S. (1985). A cognitive behavioural group treatment of bulimia. British Journal ofPsychiatry, 146, 66–69.

W. Stewart AgrasStanford University School of MedicineDepartment of Psychiatry401 Quarry Rd.Stanford, CA 94305-5722DOI: 10.1002/eat.10183

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