Scientists at Bristol University say one in 50 young people will contract Chronic fatigue Syndrome or ME at some stage. That means they have months of fatigue, typically missing a year of school and in most cases will not have any treatment.

But there is a treatment that has been shown to work - CBT or Cognitive Behavioural Therapy - and in the Netherlands they offer it over the internet with a 63% success rate. One teenage girl described on the Today programme how CBT changed her life.