Having recently endured more than a month of post-concussion fatigue, I can’t imagine how people with so-called chronic fatigue syndrome navigate through life with disabling fatigue that seemingly knows no end. Especially those who are erroneously told things like “It’s all in your head,” “Maybe you should see a psychiatrist,” or “You’d have a lot more energy if only you’d get more exercise.”

After years of treating the syndrome as a psychological disorder, leading health organizations now recognize that it is a serious, long-term illness possibly caused by a disruption in how the immune system responds to infection or stress. It shares many characteristics with autoimmune diseases like rheumatoid arthritis but without apparent signs of tissue damage.

Accordingly, doctors now typically refer to it as myalgic encephalomyelitis, meaning brain and spinal cord inflammation with muscle pain, and in scientific papers it is often written as ME/CFS. At the same time, a major shift is underway as far as how the medical profession is being advised to approach treatment.

The longstanding advice to “exercise your way out of it” is now recognized as not only ineffective but counterproductive. It usually only makes matters worse, as even the mildest activity, like brushing your teeth, can lead to a debilitating fatigue, the core symptom of the disease. Both the Centers for Disease Control and Prevention in the United States and the National Institute for Health and Care Excellence in Britain are formulating revised guidelines for managing an ailment characterized by six or more months — and sometimes years — of incapacitating fatigue, joint pain and cognitive problems.