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Analyzing Effectiveness of Long-term Psychodynamic Psychotherapy

Analyzing Effectiveness of Long-term Psychodynamic Psychotherapy To the Editor: Drs Leichsenring and Rabung1 reported that long-term psychodynamic psychotherapy (LTPP) is more effective than shorter forms of psychotherapy for complex mental disorders based on a between-group effect size of 1.8 from 7 comparative trials that they meta-analyzed. The authors did not indicate that they were concerned about this and other surprisingly large effect sizes they reported. Between-group effect sizes can be presented as group differences in terms of standard deviations or as point biserial correlations between group (eg, LTPP vs shorter-term therapies) and treatment effect. They are equivalent and convertible using a formula or tables.2 The authors, however, apparently erroneously calculated within-group pre-post effect sizes and point biserial correlations between group and within-group effect sizes, which is altogether different. It seems that they converted these correlations between group and within-group pre-post effect sizes to produce deviation-based effect sizes that do not appear reasonable. As a result, although none of the 7 studies had an overall effect size greater than 1.45, the authors reported a combined effect size of 1.8, which is statistically impossible. In a slightly larger set of 8 trials, the authors reported that LTPP had a larger overall effect than shorter-term therapies (0.96 vs 0.47) but a point biserial correlation (0.60) equivalent to a between-group effect size of 1.5. However, between-group effect sizes must be smaller than within-group effect sizes when both groups have positive effects. Similarly, these methods generated an implausible between-group effect size of 6.9 for personality functioning based on 3 trials,3-5 none of which reported an effect size for personality functioning larger than approximately 2. In addition, we believe that this collection of studies was not suitable for meta-analysis. Each reviewed study had 15 to 30 patients in the LTPP treatment group. It seems unlikely that investigators would attempt to publish a negative study with so few patients (or that such a study would be accepted for publication), which means that all published studies would have an effect size of at least 0.50 to 0.75, the minimum for statistical significance. This is an artificial floor that guarantees a large effect when these studies are combined. Back to top Article Information Financial Disclosures: None reported. References 1. Leichsenring F, Rabung S. Effectiveness of long-term psychodynamic psychotherapy: a meta-analysis. JAMA. 2008;300(13):1551-156518827212PubMedGoogle ScholarCrossref 2. McCartney K, Rosenthal R. Effect size, practical importance, and social policy for children. Child Dev. 2000;71(1):173-18010836571PubMedGoogle ScholarCrossref 3. Bachar E, Latzer Y, Kreitler S, Berry EM. Empirical comparisons of two psychological therapies: self psychology and cognitive orientation in the treatment of anorexia and bulimia. J Psychother Pract Res. 1999;8(2):115-12810079459PubMedGoogle Scholar 4. Bateman A, Fonagy P. Effectiveness of partial hospitalization in the treatment of borderline personality disorder: a randomized controlled trial. Am J Psychiatry. 1999;156(10):1563-156910518167PubMedGoogle Scholar 5. Levy KN, Meehan KB, Kelly KM, et al. Change in attachment patterns and reflective function in a randomized control trial of transference-focused psychotherapy for borderline personality disorder. J Consult Clin Psychol. 2006;74(6):1027-104017154733PubMedGoogle ScholarCrossref http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png JAMA American Medical Association

Analyzing Effectiveness of Long-term Psychodynamic Psychotherapy

JAMA , Volume 301 (9) – Mar 4, 2009

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References (21)

Publisher
American Medical Association
Copyright
Copyright © 2009 American Medical Association. All Rights Reserved.
ISSN
0098-7484
eISSN
1538-3598
DOI
10.1001/jama.2009.177
Publisher site
See Article on Publisher Site

Abstract

To the Editor: Drs Leichsenring and Rabung1 reported that long-term psychodynamic psychotherapy (LTPP) is more effective than shorter forms of psychotherapy for complex mental disorders based on a between-group effect size of 1.8 from 7 comparative trials that they meta-analyzed. The authors did not indicate that they were concerned about this and other surprisingly large effect sizes they reported. Between-group effect sizes can be presented as group differences in terms of standard deviations or as point biserial correlations between group (eg, LTPP vs shorter-term therapies) and treatment effect. They are equivalent and convertible using a formula or tables.2 The authors, however, apparently erroneously calculated within-group pre-post effect sizes and point biserial correlations between group and within-group effect sizes, which is altogether different. It seems that they converted these correlations between group and within-group pre-post effect sizes to produce deviation-based effect sizes that do not appear reasonable. As a result, although none of the 7 studies had an overall effect size greater than 1.45, the authors reported a combined effect size of 1.8, which is statistically impossible. In a slightly larger set of 8 trials, the authors reported that LTPP had a larger overall effect than shorter-term therapies (0.96 vs 0.47) but a point biserial correlation (0.60) equivalent to a between-group effect size of 1.5. However, between-group effect sizes must be smaller than within-group effect sizes when both groups have positive effects. Similarly, these methods generated an implausible between-group effect size of 6.9 for personality functioning based on 3 trials,3-5 none of which reported an effect size for personality functioning larger than approximately 2. In addition, we believe that this collection of studies was not suitable for meta-analysis. Each reviewed study had 15 to 30 patients in the LTPP treatment group. It seems unlikely that investigators would attempt to publish a negative study with so few patients (or that such a study would be accepted for publication), which means that all published studies would have an effect size of at least 0.50 to 0.75, the minimum for statistical significance. This is an artificial floor that guarantees a large effect when these studies are combined. Back to top Article Information Financial Disclosures: None reported. References 1. Leichsenring F, Rabung S. Effectiveness of long-term psychodynamic psychotherapy: a meta-analysis. JAMA. 2008;300(13):1551-156518827212PubMedGoogle ScholarCrossref 2. McCartney K, Rosenthal R. Effect size, practical importance, and social policy for children. Child Dev. 2000;71(1):173-18010836571PubMedGoogle ScholarCrossref 3. Bachar E, Latzer Y, Kreitler S, Berry EM. Empirical comparisons of two psychological therapies: self psychology and cognitive orientation in the treatment of anorexia and bulimia. J Psychother Pract Res. 1999;8(2):115-12810079459PubMedGoogle Scholar 4. Bateman A, Fonagy P. Effectiveness of partial hospitalization in the treatment of borderline personality disorder: a randomized controlled trial. Am J Psychiatry. 1999;156(10):1563-156910518167PubMedGoogle Scholar 5. Levy KN, Meehan KB, Kelly KM, et al. Change in attachment patterns and reflective function in a randomized control trial of transference-focused psychotherapy for borderline personality disorder. J Consult Clin Psychol. 2006;74(6):1027-104017154733PubMedGoogle ScholarCrossref

Journal

JAMAAmerican Medical Association

Published: Mar 4, 2009

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