The latest research on what causes chronic fatigue syndrome are testing two hypotheses. One involves previous findings that patients with CFS who have no psychiatric problems have abnormalities in the structure of their brains; the other concerns preliminary data that CFS patients have something wrong with their hearts or blood vessels.
In 1992, researchers reported evidence of inflammation in the brains of patients. Imaging scans showed pinpoint areas of swelling or loss of part of the sheath that surround nerve cells in the central nervous system scattered throughout the brain in 113 of 144 patients (78%). The abnormal areas were detected on repeat imaging and in some cases even after symptoms had eased. They are believed to be associated with a virus, but the identity is yet unconfirmed; herpes virus 6 (HHV-6) is suspected. The syndrome may in some unknown way lead to an abnormality of the immune system, which in turn reactivates a virus that has long been dormant in the body (HHV-6 infects virtually everybody in the first years of life).
A 1993 report found that chronic fatigue sufferers tend to breathe from their upper bodies, rather than from their abdomens, which results in irregular breathing and heart rate patterns. Some physicians suggested the bodies of those affected by chronic fatigue conserve energy in different ways than those of non-sufferers.
A 1995 study showed that 70% of patients had a brain stem abnormality that reduced blood flow. In other patients, not enough of the brain steroidal hormone, cortisol, was produced, and moreover the hormone did not function properly, preventing the brain from reacting to stress.
In 1995, chronic fatigue syndrome was tentatively linked to abnormalities in the regulation of blood pressure, namely neurally mediated hypotension, vasovagal syncope, vasodepressor syncope and neurocardiogenic syncope. A virus infection is a probable trigger, since not all people with abnormal blood pressure regulation develop the syndrome. An additional factor is the salt level in the diet; people who eat a lot of salt do not have the syndrome.