The chronic muscle aches, pains, and stiffness that Davidson calls fibrositis (he lists dozens of other names it has gone by) is a vague disorder with no confirming laboratory or other tests and with other symptoms as general as fatigue, irritable bowels, headaches, and depression. It is said to plague millions of Americans, is accompanied by tender points at specific muscular sites (a major criterion for diagnosis), and can be either general or specific. Though the specific form can often be traced to occupational muscle stress, Davidson puts more emphasis overall on psychological stress and attributes the condition to ""a complex interaction involving mind, body, and environment."" As for treatment and prevention, he prescribes a wide spectrum of approaches, which he summarizes in the gimmicky acronym RETRAIN (Rest and relaxation; Education; Therapeutic muscle-training, etc.). The last element ranges from stretching to massage and tai chi; and nutrition, humor, and meditation are all included under other of the headings. Oddly, some of the acronym elements are not recommended: Analgesics, Davidson says, are of limited benefit, and he avoids injections in his practice. Oddly, too, psychotherapy is not mentioned.