--- title: "Clinical summary: Researchers’ Allegiance to a Therapy Approach Biases Outcomes" description: The director of the Psychotherapy Practice Research Network (PPRNet) is Dr. Giorgio Tasca. Dr. Tasca is an Associate Professor with the School of Psychology, in the Faculty of Social, University of Ottawa. His research focus is on psychotherapy process, mechanisms of change, and outcomes, as well as eating disorders. image: https://collabzium.com/hubfs/George%20Tasca-2.jpg --- [![FAC_SOCIAL_SCIENCE_HEADER_BAR](https://collabzium.com/hubfs/FAC_SOCIAL_SCIENCE_HEADER_BAR.svg "FAC_SOCIAL_SCIENCE_HEADER_BAR")](https://www.uottawa.ca/faculty-social-sciences/) [![Collabzium](https://collabzium.com/hubfs/CollabziumLogoEnglish(Name)-COLOUR.svg "Collabzium")](https://collabzium.com/) - Articles - [Collabzium Guide](https://collabzium.com/en/articles/author/collabzium-guide) - [All articles](https://collabzium.com/en/articles) - Research - [Chairs and Labs](https://collabzium.com/en/chair-and-labs) - [About](https://collabzium.com/collabcrew) [Subscribe](https://20500402.hubspotpagebuilder.com/subscribe-now) [Subscribe](https://20500402.hubspotpagebuilder.com/subscribe-now) [PPRNET](https://collabzium.com/en/articles/tag/pprnet) # Clinical summary: Researchers’ Allegiance to a Therapy Approach Biases Outcomes [Dr. Giorgio Tasca](https://collabzium.com/en/articles/author/dr-giorgio-tasca) calendar icon Aug 07, 2024 · Reading time 2 min read [mailto:?subject=Check%20out%20https://collabzium.com/en/articles/clinical-summary-which-patients-benefit-most-from-being-matched-to-a-therapist-0-3-0-0&utm_medium=social&utm_source=email%20&body=Check%20out%20https://collabzium.com/en/articles/clinical-summary-which-patients-benefit-most-from-being-matched-to-a-therapist-0-3-0-0&utm_medium=social&utm_source=email](mailto:?subject=Check%20out%20https://collabzium.com/en/articles/clinical-summary-which-patients-benefit-most-from-being-matched-to-a-therapist-0-3-0-0&utm_medium=social&utm_source=email%20&body=Check%20out%20https://collabzium.com/en/articles/clinical-summary-which-patients-benefit-most-from-being-matched-to-a-therapist-0-3-0-0&utm_medium=social&utm_source=email) Previous [studies](https://doi.org/10.1016/j.cpr.2013.02.002) suggest that researchers tend to prefer one therapy orientation and that this preference biases the way they conduct research, the outcomes of research, and the interpretation of findings. This phenomenon is called the *researcher allegiance effect*. When researchers conduct studies comparing the efficacy of two treatments, they are more likely to find that their preferred treatment is more effective than the comparison treatment. In one [meta-analysis](https://doi.org/10.1037/a0029571), the researcher allegiance effect accounted for 12% of the difference between treatments, which is substantial. However, there is some controversy about how to understand this effect. On the one hand, it is possible that this simply reflects the tendency of researchers to have a stronger allegiance to a more effective treatment. Still, on the other hand, it could reflect a bias in which researchers consciously or unconsciously stack the deck in favour of their preferred therapy. Zimmerman and Marcus uniquely approached the question in this study to determine what drives this researcher allegiance effect. They found 19 pairs of studies (38 studies in all) in which they identified the researcher's allegiance to one of two different therapies. In each pair of studies, one research team favoured therapy A over therapy B, while in the paired study, another research team favoured therapy B over therapy A. Each paired study treated the same disorder for the same length of time. Zimmerman and Marcus then assessed if the outcomes in the paired studies differed and by how much. This approach allowed them to assess if studies of the same treatments for the same disorder had different outcomes due to different researcher allegiances. On average, for all 19 pairs, the difference was small to medium and statistically significant, ddiff = 0.35 (95% CI = 0.08–0.61; Z = 2.59, p = 0.001). The authors also rated the degree of researcher allegiance (how strongly the researcher identified with a particular therapy orientation). When they looked only at the 7 pairs of studies with the strongest researcher allegiance, the effect was notably larger and statistically significant, ddiff = 0.69 (95% CI = 0.07–0.1.31; Z = 2.19, p = 0.029). In other words, the more a researcher identified with a treatment orientation, the larger the allegiance effect favouring their preferred therapy. Overall, 22 of the 38 studies found no difference between the two treatments that were compared. ## Practice Implications Several factors could be the cause of the researcher’s allegiance effect. Researchers may be more skilled at providing (or supervising) the treatment they are allied with, may subtly express greater enthusiasm for their preferred treatment, or may select measures that are more sensitive to the outcomes of their preferred treatment. Researchers may also “spin” their findings to suggest that their preferred treatment is more effective, thus promoting conclusions that are wholly or partly inconsistent with the results. Clinicians must be cautious and skeptical when they read the results of a single study or the interpretation of a study from a secondary clinical source in which the authors claim that one treatment is superior to another. Such studies and their interpretations are inconsistent with the many [meta-analyses](https://doi.org/10.1037/0033-2909.122.3.203) showing few or no differences between time-limited manualized treatments for most disorders. > Zimmerman, J.A. & Marcus, D.K. (2024). Does researcher allegiance bias outcomes in psychotherapy research? A quasi-experimental secondary analysis. Clinical Psychology and Psychotherapy, 31, e2973. [https://doi.org/10.1002/cpp.2974](https://doi.org/10.1002/cpp.2974) To learn more about the Psychotherapy Practice Research Network, visit [www.pprnet.ca](https://collabzium.com/en/psychotherapy-practice-research-network). calendar icon Aug 07, 2024 · Reading time 2 min read [mailto:?subject=Check%20out%20https://collabzium.com/en/articles/clinical-summary-which-patients-benefit-most-from-being-matched-to-a-therapist-0-3-0-0&utm_medium=social&utm_source=email%20&body=Check%20out%20https://collabzium.com/en/articles/clinical-summary-which-patients-benefit-most-from-being-matched-to-a-therapist-0-3-0-0&utm_medium=social&utm_source=email](mailto:?subject=Check%20out%20https://collabzium.com/en/articles/clinical-summary-which-patients-benefit-most-from-being-matched-to-a-therapist-0-3-0-0&utm_medium=social&utm_source=email%20&body=Check%20out%20https://collabzium.com/en/articles/clinical-summary-which-patients-benefit-most-from-being-matched-to-a-therapist-0-3-0-0&utm_medium=social&utm_source=email) --- ### [By Dr. Giorgio Tasca](https://collabzium.com/en/articles/author/dr-giorgio-tasca) The director of the Psychotherapy Practice Research Network (PPRNet) is Dr. Giorgio Tasca. Dr. Tasca is an Associate Professor with the School of Psychology, in the Faculty of Social Sciences at the University of Ottawa. His research is centered around psychotherapy process, mechanisms of change, and outcomes, as well as eating disorders. ## Also Read - [PPRNet Clinical summary: Long-Term Effects of Psychotherapies for Depression](https://collabzium.com/en/articles/pprnet-clinical-summary-long-term-effects-of-psychotherapies-for-depression) - [PPRNet Clinical summary: Self-Compassion as a Protective Factor Against Burnout in Psychologists](https://collabzium.com/en/articles/pprnet-clinical-summary-self-compassion-as-a-protective-factor-against-burnout-in-psychologists) - [PPRNet Clinical summary: The Therapeutic Alliance in Internet-Based Interventions](https://collabzium.com/en/articles/pprnet-clinical-summary-1.-the-therapeutic-alliance-in-internet-based-interventions) - [PPRNet Clinical summary: What Do Individuals With Borderline Personalities Want From Treatment?](https://collabzium.com/en/articles/pprnet-clinical-summary-what-do-individuals-with-borderline-personalities-want-from-treatment) #### RELATED NEWS ![PPRNet Clinical summary: What 50 Years of Depression Treatment Research Has Taught Us](https://collabzium.com/hs-fs/hubfs/iStock-1206150255-1.jpg?width=600&name=iStock-1206150255-1.jpg) [PPRNET](https://collabzium.com/en/articles/tag/pprnet) ## [PPRNet Clinical summary: What 50 Years of Depression Treatment Research Has Taught Us](https://collabzium.com/en/articles/clinical-summary-which-patients-benefit-most-from-being-matched-to-a-therapist-0-3-1-0-1-2-0-0-0-1-1-2) Worldwide, about 280 million people suffer from [depression](https://linkinghub.elsevier.com/retrieve/pii/S2215036616300244?utm_source=hs_email&utm_medium=email&utm_content=2&_hsenc=p2ANqtz-9Lg7K_PytEFNh5CK1b-siVmtBdVSaEckzErb0bU0lJItZsYt7paNQ09zTIhOHxe4GtkFBnbNyt8MiFkuOrSYVPJ6vk1A&_hsmi=2), with an economic cost of nearly $1... 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