Long-term psychiatric and exercise treatments for chronic fatigue syndrome are good value for money, a study has found.
Cognitive behaviour therapy (CBT) and graded exercise therapy (GET) are both known to help patients with CFS, also known as myalgic encephalomyelitis (ME).
The new findings show that, given in addition to medical care, they are also cost effective.
Another treatment option, adaptive pacing therapy (APT), was not judged to be good value.
Researchers based their conclusions on the same criteria used by the NHS efficiency watchdog, the National Institute for health and Clinical Excellence (Nice).
Nice makes a calculation based on years lived in good health, known as quality-adjusted life years or Qalys. A treatment costing less than £20,000 to £30,000 per Qaly is believed to represent value for money.
In the study, CBT given in addition to specialist medical care was found to cost £18,374 per Qaly, GET £23,615 and APT £55,235.
Professor Paul McCrone, a health economist from King's College London, who led the new study, said: "It's very encouraging that two treatments found to help a significant number of CFS/ME patients are also cost-effective based on existing Nice criteria.
"There is now a strong case for the NHS to invest in these therapies. Our research suggests this investment would be justified in terms of improving quality of life for patients and could actually save costs to society if the impact on family members is taken into account."
CFS/ME is a complex and debilitating condition that affects around 250,000 adults and children in the UK.
Symptoms include extreme physical and mental fatigue, muscle and joint pain, disturbed sleep, and concentration and memory problems.
The new results, published in the online journal Public Library of Science ONE, are the latest from the Pace trial, funded by the Medical Research Council.
The trial began in 2005 and recruited 640 patients. It compared four of the main treatments available for people with CFS/ME, specialist medical care, CBT, GET and APT.
CBT helps patients understand how to affect their symptoms by thinking about them differently. GET involves a tailored exercise programme taking into account a patient's fitness and symptoms.
APT is an occupational therapy approach that matches a patients' activity level to the amount of energy they have.
Early findings from the trial reported last year showed that CBT and GET could benefit 60% of patients for whom fatigue was the main symptom.
The latest study looked at cost effectiveness over a period of one year.
Specialist medical care was the cheapest single option. But when benefit to quality of life was taken into account, medical care plus CBT became the most cost-effective treatment followed by GET.