C FS is baffling with no known cause but a lot of theories, ranging from chemical reactions to psychological disorders.
Doctors often misdiagnose it as depression.
The latest study compared 51 Gulf War vets with CFS symptoms with 42 veterans without symptoms and found a distinctive difference in blood pressure reactions. Those with CFS symptoms showed lower blood-pressure responses in two mental stress tests, which indicates a suppression of cardiovascular responses. However, in a third test intended to detect differences in reflex responses to physical sensations, both groups of vets did about the same. In that test, a plastic bag filled with crushed ice and water was placed on the participants' foreheads, while their blood pressure was measured. The stress of the mental efforts tests, which included math and speech tests, were expected to raise blood pressure.