Like [Jean Harrison], many people with chronic fatigue are first told they have depression. But the afflictions are quite different - for example, depression triggers an increase in the stress hormone cortisol, while chronic fatigue produces a decline, said Harvard's [Anthony Komaroff]. While depression gets better with drugs such as Prozac, the fatigue of CFS does not.
Harrison's perplexing response to exercise is also typical of many chronic fatigue patients - exercise triggers the release of fatigue-inducing immune chemicals called cytokines. People with the disease sometimes can exercise as hard as healthy people, but they feel awful for a day or two afterward, [William Reeves] said.
In research published last spring, Christopher Snell at the University of the Pacific in Stockton, Calif., showed that some people with chronic fatigue syndrome experience a flare-up of symptoms after exercise. Paradoxically, though, a 2004 analysis of data pooled from five separate studies showed that very gradual increases in aerobic exercise can reduce fatigue in some patients.