Researchers say they've pinpointed a possible culprit in chronic fatigue syndrome (CFS), reporting that an overactive immune system might send the entire body into an overwhelming state of exhaustion.
"For the first time, we have shown that people who are prone to develop a CFS-like illness have an overactive immune system, both before and during a challenge to the immune system," said lead researcher Alice Russell, from King's College London.
"Our findings suggest that people who have an exaggerated immune response to a trigger may be more at risk of developing CFS," Russell added.
People with chronic fatigue syndrome -- also called myalgic encephalomyelitis -- experience extreme tiredness. The causes of the condition remain unclear, but many patients say their condition began after their immune system fought off an infection.
One problem in trying to determine the causes of chronic fatigue syndrome is that it's impossible to assess patients before the illness develops. In this study, researchers used a model for chronic fatigue syndrome based on the hepatitis C treatment interferon-alpha.
Interferon-alpha triggers immune system activity in much the same way as a major infection does, the study authors explained in a college news release. Many patients who receive interferon-alpha develop acute fatigue during treatment and some have fatigue that lasts for more than six months after treatment ends.
In the new study, the researchers assessed fatigue and immune system activity in 55 patients before, during and after treatment with interferon-alpha. The investigators discovered differences between the immune systems of 18 patients who developed long-term fatigue and those who had a normal recovery.
Those 18 patients had a much stronger immune response during treatment with interferon-alpha, with a doubling in the levels of immune system messenger molecules called interleukin-10 and interleukin-6, according to the report.
Even before treatment started, levels of interleukin-10 were higher among the 18 patients who later developed long-term fatigue, suggesting the immune system may have been primed to overreact, the study authors explained.
Yet, there was no difference before treatments between the groups in their levels of fatigue or in psychiatric symptoms, like depression or recent stressful events, the scientists noted.
The study findings were published Dec. 17 in the journal Psychoneuroendocrinology.
According to senior researcher Carmine Pariante, "A better understanding of the biology underlying the development of CFS is needed to help patients suffering with this debilitating condition. Although screening tests are a long way off, our results are the first step in identifying those at risk and catching the illness in its crucial early stages."
Further research is needed to confirm that the findings from patients treated with interferon-alpha would also apply to people with chronic fatigue syndrome, and to better understand the factors that may be driving an exaggerated immune response, the study authors said.