There is great variation in the severity and duration of symptoms and it is not possible to accurately predict recovery for individuals.

In both adults and children it appears that the prognosis is worse for the most severe cases. It also appears that early diagnosis may lessen the impact of the illness and that those with acute onset have a better prognosis than those with a gradual onset (CFS/ME Working Group 2002, p.39).

Most will improve to some degree over time and some recover well but a number of studies have indicated that less than 10% of adults regain their their pre-illness level of functioning. There is a tendency for the course of the illness to plateau from between six months and six years although some experience a fluctuating course of relative remission and relapse. Some become severely and possibly permanently disabled and some experience progressive deterioration (CFS/ME Working Group 2002, p. 7).

The prognosis for children is often better than for adults (Bell, 2001). The illness appears not to last as long and a high proportion seem to recover, though recovery may not be complete and relapse in adulthood may occur.

"Overall there is wide variation in the duration of illness, with some people recovering in less than two years while others remain ill for decades. Those who have been affected for several years seem less likely to recover; full recovery after symptoms persist more than five years is rare." (CFS/ME Working Group 2002, p. 7)

More information:

CFS/ME Working Group (2002) 'A report to the Chief Medical Officer of an Independent Working Group', Department of Health, London.

Bell, D. S. et al (2001) 'Thirteen-year follow-up of children and adolescents with chronic fatigue syndrome', Pediatrics, May, 107 (5), 223 -233.