Home > Encyclopedia of Mental Disorders > Fatigue

Introduction

Fatigue may be defined as a subjective state in which one feels tired or exhausted, and in which the capacity for normal work or activity is reduced. There is, however, no commonly accepted definition of fatigue when it is considered in the context of health and illness. This lack of definition results from the fact that a person's experience of fatigue depends on a variety of factors. These factors include culture; personality; the physical environment (light, noise, vibration); availability of social support through networks of family members and friends; the nature of a particular fatiguing disease or disorder; and the type and duration of work or exercise. For example, the experience of fatigue associated with disease will be different for someone who is clinically depressed, is socially isolated, and is out of shape, as compared to another person who is...