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
