What are the latest research findings?

The most significant recent finding is that CFS appears to be associated with a cardiac abnormality known as 'neurally mediated hypotension' (NMH). This condition is well known to cardiologists, and involves a mis-communication between the heart and the brain which causes an abnormal lowering of blood pressure, leading to symptoms such as fatigue, dizziness and nausea. Preliminary studies have indicated that a majority of people with CFS suffer from NMH, and some respond well to treatment. To better assess the association between CFS and NMH, and to explore potential treatment options, researchers from Johns Hopkins University and the National Institute of Allergy and Infectious Diseases in the USA are currently undertaking a large study. The researchers do not believe that NMH is the cause of CFS, or that it is reponsible for all symptoms.

In published studies looking at immune system functioning in CFS, immune system abnormalities have been found in most patients. Activation of the immune system - as if it were responding to a foreign organism - is consistently reported. Also consistently reported is poor functioning of natural killer cells, which are important as a first line of defence against viruses. There is now some evidence of abnormal production of cytokines (immune system chemicals) in people with CFS. However, no specific abnormality has yet been found in all people with CFS. Studies of muscles conducted at different centres indicate that muscle function is normal in CFS.

Sleep disturbance, documented in laboratory studies, has been recognised as an important feature of the syndrome. In the last few years, studies reporting abnormalities in hormonal levels and neurochemicals have appeared, opening up new avenues for research. Several reports of SPECT scans (a brain imaging technique) have been published, showing reduced blood flow and/or altered cellular metabolism in regions of the brain in people with CFS.

Magnetic resonance imaging (MRI - another brain imaging technique) has revealed 'unidentified bright objects' in the brain in a significant percentage of people with CFS. In tests of memory and concentration, people with CFS perform more poorly in particular aspects than healthy people, and people with some other diseases.

Biochemical studies have documented metabolic disturbances in CFS, for example abnormalities in blood levels of angiotensin-converting enzyme (ACE) and acyl-carnitine.

Research into CFS is still in its very early stages when compared with other diseases. Published research studies - while few in number - have generally been of high quality. Research is now focusing on the immune system, the brain, metabolic factors and the role of viruses in CFS.