Overview

Chronic fatigue syndrome (CFS) is a complicated disorder characterized by extreme fatigue that lasts for at least six months and that can't be fully explained by an underlying medical condition. The fatigue worsens with physical or mental activity, but doesn't improve with rest.

Other characteristic symptoms include:

• Sleep that isn't refreshing
• Difficulties with memory, focus and concentration
• Dizziness that worsens with moving from lying down or sitting to standing

This condition is also known as myalgic encephalomyelitis (ME). Sometimes it's abbreviated as ME/CFS. The most recent term proposed is systemic exertional intolerance disease (SEID).

The cause of chronic fatigue syndrome is unknown, although there are many theories — ranging from viral infections to psychological stress. Some experts believe chronic fatigue syndrome might be triggered by a combination of factors.

There's no single test to confirm a diagnosis of chronic fatigue syndrome. You may need a variety of medical tests to rule out other health problems that have similar symptoms. Treatment for chronic fatigue syndrome focuses on improving symptoms.