LONDON, Oct 17 (Reuters) - A respected science journal is to withdraw a much-cited review of evidence on an illness known as chronic fatigue syndrome (CFS) amid fierce criticism and pressure from activists and patients.

The decision, described by the scientists involved as “disproportionate and poorly justified”, is being seen as a victory for activists in a research field plagued by uncertainty and dispute over whether CFS, also known as myalgic encephalopathy (ME), has physical and psychological elements.

Emails seen by Reuters show editors at the influential Cochrane Review journal asking researchers who conducted the analysis, which was published in April 2017, to agree to it being temporarily withdrawn.

They also ask the review’s authors to agree to a statement saying their analysis requires “further work in response to feedback and complaints”.

Published on the Cochrane Database of Systematic Reviews, Cochrane’s evaluations are considered a gold standard in scientific literature and known internationally as dispassionate analyses of the best evidence on a given subject.

It is unusual for Cochrane to withdraw a review without the authors’ agreement and unless new scientific evidence emerges for inclusion in an update.

Research into CFS and ME, widely referred to by the joint acronym CFS/ME, is highly contentious -- in part because the illness is poorly understood. It is a severe, chronic illness characterized by long-term physical and mental fatigue.

Patient groups in the United States, Europe, Australia and elsewhere often challenge each other about the nature of the disorder, how it should be diagnosed and whether it can be treated. Scientists conducting studies on potential therapies say they are often harassed and verbally abused by groups that disagree with their approach.

Colin Blakemore, a professor of neuroscience and philosophy at London University’s School of Advanced Studies, said the withdrawal decision set a worrying precedent for scientific evidence being over-ridden by the opinions of activists.

The withdrawal would also be “a departure from the principle that has always guided Cochrane reviews -- that they should be based on scientific and clinical evidence ... but not influenced by unsubstantiated views or commercial pressures.”

Blakemore has no affiliation with the Cochrane review authors and has not conducted studies in CFS/ME, but he experienced lobbying by activists when he was chief executive of Britain’s Medical Research Council from 2003 to 2007.

EVIDENCE

The review at the center of this dispute, written by a team headed by Lillebeth Larun, a scientist at the Norwegian Institute of Public Health, looked at eight randomized controlled studies of exercise therapy as a treatment for patients with CFS/ME.

Graded exercise therapy involves taking a patient’s activity level right back to a minimum, and then gradually increasing it within their capability.

The review found “moderate quality evidence” to show the approach can help some CFS/ME patients, concluding: “Exercise therapy had a positive effect on people’s daily physical functioning, sleep and self-ratings of overall health.”

But in an email seen by Reuters, Cochrane editors Rachel Churchill and David Tovey say the review had received “extensive feedback” which they now considered grounds for it to be temporarily removed.

Tovey confirmed to Reuters that he had made a decision to withdraw the review temporarily, saying this would give the authors time to respond to several points in a complaint which “we felt ... raised issues we needed to address”.

“This not about patient pressure,” he added in a telephone interview. “This was a decision we reached with difficulty because we know the incredibly challenging environment this review sits in.”

In their Oct. 15 email, addressed to Larun, Churchill and Tovey wrote: “We are ... temporarily withdrawing your review to allow you and your co-authors time to adequately address the feedback received. Consequently, your review will shortly be removed from the Cochrane Library.”

Larun told Reuters she was “extremely concerned and disappointed” with the Cochrane editors’ actions. “I disagree with the decision and consider it to be disproportionate and poorly justified,” she said.

In an emailed response to questions from Reuters, Tovey said: “We are in discussion with the review author team about this review following a formal complaint to me as Cochrane’s editor in chief, which we judged to raise important questions.”

Larun said she would not characterize this as a discussion, but as a unilateral decision made by Cochrane editors.

“ANTAGONISTIC”

CFS/ME is thought to affect as many as 2.5 million people in the United States and around 250,000 people in Britain, although estimates vary widely due to a lack of formal diagnostics.

The condition can bring crushing fatigue, joint pain, headaches and sleep problems and can render patients bed- or house-bound for years. While the cause is a mystery, some theories point to a viral trigger.

On treatments, evidence from at least 10 published studies -- including the 2017 Cochrane Review -- shows psychological approaches such as graded exercise and cognitive behavioral therapy can help some CFS/ME patients improve.

Yet critics say this amounts to a suggestion that the syndrome is a mental disorder, or “all in the mind”. They campaign fiercely to block or discredit any research looking at psychological or behavioral treatments, arguing that they are physically, not psychologically, debilitated.

Tovey and Churchill said in their email to Larun that “in response to concerns raised by members of the CFS community” they are considering moving responsibility for research reviews on CFS/ME away from their mental health department into another section -- possibly the “long-term conditions” section.

Categorizing CFS/ME under mental health disorders “has been antagonistic to some in the CFS community, potentially impacting on the confidence people have in our reviews”, they wrote.

Blakemore said this was a sign of Cochrane’s editors sidelining evidence under pressure from CFS/ME campaigners who insist their illness is a physical disease and not a psychological disorder.

He also warned of the risk of wider effects on all patients if a respected scientific journal like Cochrane “capitulates” to lobbying from small numbers of vocal patient campaign groups.

“This could change medical practice,” he said. “And that could mean that patients with this very serious condition are denied access to treatments that might help them, and which evidence suggests can help some of them.”

On the decision to move CFS/ME work out of the Cochrane’s mental disorders section, Tovey confirmed to Reuters that this was made in response to feedback from CFS/ME patients and campaigners.

CFS/ME is a “complex” disorder and categorizing it in the mental health section “clearly causes some offense”, he said.