The Times today publishes Lynn Gilderdale's own account of the Chronic Fatigue Syndrome or ME that she had suffered from since she was 14. Her mother Kay was unanimously cleared by a jury yesterday of attempted murder for assisting 31-year-old Lynn's suicide. Written only a few months before her death, Lynn's description of her determined wish to commit suicide makes for extremely sad reading. It also demonstrates to sceptics that Chronic Fatigue Syndrome, once mocked as "yuppie flu", is for some a real and catastrophic disorder.

About a quarter of people diagnosed with CFS or ME experience the debilitating symptoms described by Lynn - confined to bed, unable to feed except through a tube, unable to care for herself without help, her bones weakened by osteoporosis. Lynn's suffering is bad enough but one also struggles to comprehend the torment her parents and her brother must have suffered for the 17 years that she was ill.

Discussion of what causes CFS is an incredibly delicate area because feelings run so high. One thing I find a bit irritating, though, is the obsession with finding a physical cause. Whenever you hear the many vocal and articulate advocates for the illness on Woman's Hour, for instance, they talk as if CFS can only be "real" and bona fide and respectable if it's a 100 per cent physical illness. They sometimes talk as if mental illnesses aren't equally real and that's insulting to the mentally ill. (I don't think the confusion over nomenclature helps matters, either. ME (myalgic encephalomyelitis) might sound authentically scientific, but it describes something - inflammation of the brain and spinal cord - that isn't actually seen very often in sufferers.)

CFS advocates sometimes imply that if the illness was shown to be psychogenic, it would be tantamount to saying it was "all in the mind" and therefore imaginary. But mental illnesses are not imaginary just because they affect the brain, where the mind is based. They're really just as much a matter of biology as so-called physical illnesses. The only difference is that mental illnesses involve the brain, which is a physical thing, as well as the mind, which is more of an idea. I am not, repeat not, saying there isn't a physical cause for CFS - there may well be. I'm just saying it would not make it any less real if in some cases it was shown to originate in the brain. It is a mistake to underestimate the power of the brain to affect the body.

Action for ME can be found at www.afme.org.uk