Chronic fatigue syndrome: 3 cases and a discussion of the natural history of attention-deficit/hyperactivity disorder.

Fatigue is commonly reported in the primary care setting; however, its cause is often unclear. This article presents 3 cases involving patients with chronic fatigue syndrome who responded poorly to treatment. After clinical evaluation, all patients were found to meet criteria for attention-deficit/hyperactivity disorder (ADHD) and underwent a standard regimen of a psychostimulant medication. After treatment with psychostimulants, the 3 patients reported improved symptoms of fatigue and pain, and cognitive and core ADHD symptoms. These cases suggest that ADHD and chronic fatigue syndrome (and possibly fibromyalgia) share a common underlying mechanism. This article presents a model suggesting that over time, ADHD (predominantly inattentive type) develops into a syndrome of chronic fatigue and pain. These cases indicate that fatigue may be an important presenting symptom of adult ADHD. These cases also suggest the need for additional research to determine the prevalence of ADHD in patients who present with fatigue, and, in those meeting criteria for ADHD, the responsiveness of fatigue to psychostimulant treatment.