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. 2012 Jul;45(5):670-6.
doi: 10.1002/eat.22009. Epub 2012 Mar 12.

How many therapists? Practical guidance on investigating therapist effects in randomized controlled trials for eating disorders

Doug Thompson  1 , Fary Cachelin, Ruth H Striegel-Moore, Bruce Barton, Munyi Shea, G Terence Wilson
Affiliations

How many therapists? Practical guidance on investigating therapist effects in randomized controlled trials for eating disorders

Doug Thompson et al. Int J Eat Disord. 2012 Jul.

Abstract

Objective: An important question in implementation/dissemination research is whether the efficacy of a given treatment varies in part based on the therapist delivering the treatment. This study sought to provide practical guidance to researchers in the field of eating disorders for building measurement of therapist effects into the design of a typical, relatively small randomized controlled trial (RCT).

Method: Using assumptions based on past trials of eating disorder treatments, Monte Carlo simulations were used to examine 12 different scenarios based on crossing the number of therapists (between two and five) and the estimated therapist effect size (small, medium, and large). Patient sample size and study design were held constant.

Results: There was reasonable power (≥70%) to detect the therapist effect with three or four therapists and a large effect size.

Discussion: Several practical implications for testing therapist effects in RCT are discussed.

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References

    1. Loeb KL, Wilson GT, Labouvie E, Pratt EM, Hayaki J, Walsh BT, et al. Therapeutic alliance and treatment adherence in two interventions for bulimia nervosa: A study of process and outcome. J Consult Clin Psychol. 2005;73:1097–1107. - PubMed
    1. Webb CA, DeRubeis RJ, Barber JP. Therapist adherence/competence and treatment outcome: A meta-analytic review. J Consult Clin Psychol. 2010;78:200–211. - PMC - PubMed
    1. Wilson GT, Wilfley DE, Agras WS, Bryson S. Allegiance bias and therapist effects: Results of a randomized controlled trial of binge eating disorder. Clin Psychol: Sci Pract. 2011;18:119–125. - PMC - PubMed
    1. Crits-Cristoph P, Mintz J. Implications of therapist effects for the design and analysis of comparative studies of psychotherapies. J Consult Clin Psychol. 1991;59:20–26. - PubMed
    1. Jannoun L, Munby M, Catalan J, Gelder M. A home-based treatment program for agoraphobia: Replication and controlled evaluation. Behav Ther. 1980;11:294–305.

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