Conflicts of interest in Cochrane reports on psychological interventions


Recently I was honored to join an esteemed group of international colleagues in writing to the Cochrane about the Collaboration’s inattention to conflicts of interest in reviews of psychotherapeutic interventions.

The Collaboration has been particularly lax in dealing with conflicts of interest with respect to psychological interventions for “chronic fatigue syndrome” and medically unexplained symptoms. The group obviously don’t apply the same standards that they would to industry’s involvement in evaluations of medical interventions. Why should psychotherapy be different?

In 2017 I will push the Cochrane to do a better job of protecting their valuable reviews from the taint of conflicts of interest, both declared and undeclared.

For background, please see my previous posts –

An open letter to the Cochrane Collaboration: Bill Silverman lies a-moldering in his grave

Why the Cochrane Collaboration needs to clean up conflicts of interest

 I elicited a reply from David Tovey, the Editor in Chief of the Cochrane Library:

To which I responded:

My response to an invitation to improve the Cochrane Collaboration by challenging its policies

The letter with an international group of psychotherapy researchers and meta-analysts

Conflicts of interest in Cochrane reports on psychological interventions

Winfried Rief  (GER), Gerhard Andersson A(SWE), Juergen Barth (SWI), James Coyne (US), Pim Cuiipers (NL), Stefan G. Hofmann  (USA), Klaus Lieb (GER)

Conflicts of interests are a major threat to the validity of clinical trials, meta-analyses and Cochrane reports. Accordingly, people with close links to pharmaceutical companies such as Novartis are typically not invited to chair a Cochrane review on methylphenidate in ADHD, members of Pfizer are not chairing Cochrane reports on sildenafil, etc. However, Cochrane analyses on psychological interventions allow strong conflicts of interests of the chairing experts. Conflicts of interests in psychotherapy might be responsible for controversial and heated debates beyond scientific evidence, and financial involvements and interests can be also substantial 1.

The influence of personal preferences in original clinical trials is strong and a robust finding. This well-known influence is often called the allegiance effect. If experts are highly identified with a specific treatment approach, their scientific reports notoriously overestimate the effect sizes of this treatment. A recent analysis showed a robust and moderate allegiance effect on outcome reports (Cohen’s d=.54) 2. If meta-analyses aggregate these biased original study reports, again mainly steered by the same scientists who are over-identified with this approach, the bias is further amplified in the corresponding Cochrane analysis.

Therefore, we discourage that authors with a strong allegiance for one therapeutic intervention analyze and summarize their favorite approach in Cochrane reports. For example, the person who co-developed cognitive therapy (Aaron T. Beck) should not write the Cochrane analysis on cognitive therapy; Steven Hayes should not author a Cochrane analysis on Acceptance and Commitment Therapy, which was primarily  developed by himself, and for which he expressed a serious interest that this should be broadly disseminated; Gerhard Andersson should not review internet interventions, after a major part of published trials in this field originate from his group; Peter Fonagy and Falk Leichsenring should not chair Cochrane reviews on psychodynamic psychotherapies, after they published a series of papers all expressing a strong interest that these types of therapies should be better acknowledged.

Two conclusions can be drawn. First, the most ambitious proponents for specific treatments should not have a major influence in Cochrane reports on this intervention. Existing Cochrane reports fulfilling this criterion should be excluded from the Cochrane databases. Second, conflicts of interests of any expert who contributes to Cochrane analyses of psychological interventions should be assessed by the Cochrane group and declared by the authors. Criteria for this type of conflict of interest that should be reported could be: the author developed one of the treatments that is examined in the meta-analysis; the author wrote a treatment manual that is examined in the meta-analysis; the author gave workshops or keynote lectures on one of the treatments or is leading a respective psychotherapy institute; the author published comments in favor of one of the treatments or recommended one of the treatments over another; original studies of the author are included in the Cochrane report.

As far as we understood the Cochrane initiative, it is supposed to provide robust and critical information to the public and to health care providers. However, this can only be achieved if no obvious conflicts of interest of the authors are evident, or if conflicts of interest are balanced between proponents and more critical participants. While the Cochrane initiative started already attempts to control for allegiance effects, these effects need to be controlled more rigorously. All authors should declare potential conflicts of interest for reasons of transparency, while experts with strong allegiance to one treatment should not be included in Cochrane reports about this treatment at all.


  1. Lieb K, von der Osten-Sacken J, Stoffers-Winterling J, Reiss N, Barth J. Conflicts of interest and spin in reviews of psychological therapies: a systematic review. BMJ Open 2016; 26(6 (4)).
  2. Munder T, Brütsch O, Leonhart R, Gerger H, Barth J. Researcher allegiance in psychotherapy outcome research: An overview of reviews. Clinical Psychology Review 2013; 33: 501-11.

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