From Expert System: Chronic Fatigue
Clinical depression,whether reactive or due to an underlying psychiatric disorder is often associated with the complaint of fatigue or exhaustion. Associated symptoms include lack of concentration, weight loss or weight gain, insomnia, impaired job or school performance, and loss of sexual desire.
Many factors may be involved in precipitating depression, for example, disappointment, sadness, or despair resulting from significant life events such as death of someone close, separation, divorce, loss of a job, etc. Sometimes various "thresholds," such as moving, changing jobs, leaving home, getting married, entering college, other stressful life events, such as surgery, a disabling accident, or even reaching a milestone in age, conspire to induce or edge a person into clinical depression.
Fatigue in cases with an emotional or psychogenic background is usually a secondary symptom masking the true problem, a reactive or major depressive illness.
For more information, try the Depression Module.