What Is Chronic Fatigue Syndrome?

Chronic fatigue ­syndrome, also called myalgic enceph­alomyelitis (ME/CFS), is different from ordinary exhaustion that improves with rest and time. It’s marked by unrestful sleep, brain fog, and debilitating fatigue that lasts at least six months. Symptoms often worsen after any kind of exercise, which is known as post-exertional malaise, or PEM.

There’s no definitive diagnostic test for ME/CFS, and its underlying cause is an area of active study (some research points to immune dysfunction). While treatment can be challenging and there’s no one-size-fits-all cure, most guidelines emphasize symptom care and energy management — also known as pacing — to prevent boom-and-bust crashes.

Some clinicians advocate for nervous-system regulation techniques to help moderate stress tolerance, followed by personalized steps to address sleep, pain, and orthostatic symptoms. This approach aims to calm physiological overload and restore autonomic balance and day-to-day function.