The main characteristic of ME/CFS is a worsening of symptoms following physical, emotional or mental activity with a prolonged recovery time, generally at least a day but sometimes weeks or months. The worsening can be delayed 24 hours or more.

The amount of activity that can be carried out before symptoms worsen varies from person to person according to overall illness severity and over time.

Living within one's fluctuating activity limits (through, for example pacing) is generally considered the key aspect of managing ME/CFS - there is some evidence that it may lead to an improvement. Going beyond personal activity limits too much and too often can delay recovery and lead to a long-lasting increase in illness severity.

Levels of severity

The mildly affected may be able to work or study full-time but with considerable personal effort and organisational adjustments (such as flexible working hours and help with domestic tasks) and little recreational activity.

With a greater severity of symptoms, part-time work or study may be all that is possible without seriously exacerbating symptoms. The fluctuating nature of symptoms (fluctuating from hour to hour and day to day) makes it difficult to plan ahead with certainty - regular attendance and meeting strict deadlines can be a problem. Students may require special arrangements for attendance, assignments and exams.

Walking distances, climbing stairs, bending and lifting, carrying bags, prolonged sitting, standing still and repetitive actions can often worsen symptoms, making difficult certain types of employment, the use of public transport and activities such as supermarket shopping. Many people with ME/CFS find driving physically and cognitively debilitating and can only manage short distances before symptoms worsen significantly - they are often dependent on family, friends and taxis for transport.

Environments where there are bright lights, high noise levels, perfumes and air pollutants are sometimes a problem for people with ME/CFS, as can be jobs requiring multi-tasking, calculations, prolonged writing or prolonged computer and/or telephone use.

The moderately severely affected are too ill to work or attend school and may require help with personal care and the tasks of normal daily living, such as washing, housework, shopping and cooking. For some, distance education may be an option.

The severely affected are rarely well enough to leave the home and may need wheelchairs for mobility. They may be in bed for much of the time. Social isolation can become a problem, with previous social contacts often falling away when illness is prolonged.

The very severely affected are totally dependent on others and experience additional, severe symptoms such as seizures, partial paralysis and gastro-intestinal paresis and may require tube-feeding.

Illness severity and disability are often increased when conditions such as multiple chemical sensitivity and fibromyalgia co-exist with ME/CFS.

People with ME/CFS can often look well - it be hard for others to appreciate how they are feeling. When "out and about" people with ME/CFS are at their best and keen to be as active and "normal" as possible. The planning and effort that is likely to have gone into making the activity possible is not evident, nor is how long it will take to recuperate. At their worst, people with ME/CFS are at home and not in public view. People other than the immediate family can be unaware of the degree to which ME/CFS can be debilitating.

Health and welfare professionals, employees, relatives and friends can assist people with ME/CFS by showing understanding of this chronic, difficult to manage, debilitating and often invisible illness.

Categories of severity

Cox D. L. and Findley L.J. (1998) have suggested the following:

Mild - Are mobile and can care for themselves and can do light domestic tasks with difficulty. The majority will still be working. However, in order to remain in work, they will have stopped all leisure and social pursuits, often taking days off. Most will use the weekend to rest in order to cope with the week.

Moderate - Have reduced mobility and are restricted in all activities of daily living, often having peaks and troughs of ability, dependent on the degree of symptoms. They have usually stopped work and require rest periods, often sleeping in the afternoon for one to two hours. Sleep quality at night is generally poor and disturbed.

Severe - Will be able to carry out minimal daily tasks only, face washing, cleaning teeth, have severe cognitive difficulties and be wheelchair dependent for mobility. These people are often unable to leave the house except on rare occasions with severe prolonged after-effect from effort.

Very severe - Will be unable to mobilise or carry out any daily tasks for themselves and are in bed for the majority of the time. These people are often unable to tolerate any noise and are generally extremely sensitive to light.

More information:

Cox D. L. and Findley L.J. (1998) 'Management of chronic fatigue syndrome in an inpatient setting: Presentation of an approach and perceived outcome', British Journal of Occupational Therapy, vol. 61, pp. 405-409.

Fact Sheet 4: Learning to pace