By Anne Harding

NEW YORK (Reuters Health) - New research confirms that emotional and sexual abuse in childhood are important risk factors for chronic fatigue syndrome (CFS).

Individuals who reported moderate to severe levels of sexual abuse, emotional neglect, and emotional abuse in childhood were nearly six times as likely to have CFS compared to people who didn't experience maltreatment in early life, researchers report in the January issue of the Archives of General Psychology.

Dr. Christine Heim of Emory University School of Medicine in Atlanta and her colleagues also found that CFS patients who had experienced maltreatment as children had abnormally low levels of cortisol, a hormone the body needs in order to mount a healthy response to stress. Cortisol secretion was normal in the patients who weren't abused in childhood.

Cortisol is "good to have during stress," Heim explained in an interview. The hormone controls how the body metabolizes energy when stress strikes, and also influences immune function. Having too little cortisol -- or too much -- can signal an impaired ability to cope with stress.

"It's all about having the right balance, and childhood trauma could be more like a general risk factor that interferes with the body's ability to maintain balance," she added.

Patients with CFS suffer from debilitating fatigue that doesn't get better with rest, and may be worsened by physical or mental activity, according to the Centers for Disease Control and Prevention's website. Other symptoms can include joint and muscle pain and memory problems and difficulty concentrating.

In a previous pilot study of Wichita, Kansas residents, Heim and her team had uncovered a link between childhood trauma and CFS risk. In the current study, they compared 113 people with CFS and 124 "controls" without the disorder.

Among the CFS patients, 62 percent had experienced at least one type of childhood trauma, such as sexual, physical or emotional abuse, or emotional or physical neglect, compared to 24 percent of the control group.

Any trauma exposure increased the likelihood of developing CFS 5.6-fold, and the risk rose with the number of types of childhood maltreatment a person reported.

Normally, a person's cortisol levels climb when they wake up in the morning. Overall, this cortisol awakening response was "flattened" among the CFS patients. However, when the researchers separated out the CFS patients who also reported childhood trauma, they found they were the only group with abnormally low levels of the hormone. Levels in those with no history of trauma who had CFS were the same as those of the control patients.

Not all of the CFS patients in the study had experienced childhood abuse, Heim pointed out, so there is likely another mechanism that caused the syndrome in these patients -- for example, a combination of genetic vulnerability and infection.

Nevertheless, she added, the findings underscore the importance of seeing CFS as a condition with both psychological and biological roots.

SOURCE: Archives of General Psychiatry, January 2009.

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