Causes of chronic fatigue syndrome 

Exactly what causes chronic fatigue syndrome (CFS) is unknown, but there are several theories.

Some experts think a viral infection such as glandular fever can trigger the condition. Tiredness is normal after a viral infection, but this does not explain why symptoms persist and get worse in CFS.

Also, many cases of CFS do not start after an infection and this theory does not explain why the condition sometimes develops gradually.

Other suggested causes of CFS include:

  • problems with the immune system  
  • a hormone imbalance 
  • psychiatric problems – some cases have been linked to mental exhaustion, stress, depression and emotional trauma
  • genes – some people may have an inherited tendency to develop CFS, as it is more common in some families
  • traumatic events - some cases have been linked to events such as surgery or a serious accident

It is possible that CFS is caused by a combination of factors. Further research is necessary to confirm the cause(s).

Debate over classification

The World Health Organization (WHO) has classified CFS as a chronic (long-term) neurological condition and this classification has been accepted by the Department of Health.

However, the WHO’s decision remains controversial and is not accepted by everyone working in the field.

Members of the team of health professionals who drew up the National Institute of Health and Care Excellence (NICE) guidelines for CFS could not agree that this classification is the right decision, and 84% of members of the Association of British Neurologists surveyed in 2011 said they did not view CFS as a neurological condition.

Page last reviewed: 20/03/2013

Next review due: 20/03/2015