What are some of the treatment regimens that sufferers of chronic fatigue syndrome should follow? Many major medical organizations cite two: psychotherapy and a steady increase in exercise. There’s just one problem. The main study that has been cited as proof that patients can recover with those treatments overstated some of its results. In reality, the claim that patients can recover from these treatments is not justified by the data.

That’s the finding of a peer-reviewed preliminary re-analysis of previously unpublished data from the clinical trial, the largest ever for chronic fatigue syndrome. Nicknamed the PACE trial, the core findings of the British study appeared in The Lancet in 2011 and Psychological Medicine in 2013. Patients battled for years to obtain the underlying data, and last spring, a legal tribunal in Britain, the General Regulatory Chamber, directed the release of some of the study’s information.

The impact of the trial on treatment options for the estimated one million chronic fatigue patients in the United States has been profound. The Mayo Clinic, Kaiser Permanente, WebMD, the American Academy of Family Physicians and others recommend psychotherapy and a steady increase in exercise.

But this approach can be harmful. According to a 2015 report from the Institute of Medicine, now the National Academy of Medicine, even minimal activity can cause patients prolonged exhaustion, muscle pain, cognitive problems and more. In severe cases, a short conversation or a trip to the bathroom can deplete patients for hours, days or more. In surveys, patients routinely report deterioration after a program of graded exercise. The psychotherapeutic intervention also encourages patients to increase their activity levels.