Stress
There is some evidence that stress may trigger CFS in people who are at risk for the disease because of genetic factors. People who experienced trauma during childhood -- including sexual and emotional abuse -- are significantly more likely to develop CFS than those who did not experience any trauma. Researchers say the stress of abuse may trigger the condition through its effects on the central nervous system, immune system, and neuroendocrine system (which is related to both nerves and hormones). However, most people who experience childhood trauma do not go on to develop CFS.

Depression and Psychological Factors
Depression is very common in the general population. It affects up to one-fifth of all Americans at some point in their lives, and most depressed people feel fatigued. The link between psychological disorders and chronic fatigue syndrome is problematic because so many of the symptoms overlap. The rates of depression are very high in CFS patients, possibly higher than in patients with other conditions (notably fibromyalgia and multiple chemical sensitivity).

Depression can lead to suicide, which may explain the increased suicide rate in people with CFS. For this reason, depression should be diagnosed and treated promptly in patients with CFS. Studies report that most children and adolescents with CFS have psychiatric disorders. Psychological factors in childhood may increase the risk of developing CFS later in life.

Age and Gender
People who are in their 40s and 50s most often experience chronic fatigue. Studies have found that four out of five people with CFS are women, although women do not appear to have more severe symptoms than men with the disorder. Children and adolescents can also have CFS, although it is less common than in adults. Most studies indicate that girls are more likely than boys to develop CFS.