The study, led by researchers at the Institute of Genetics and Cancer, examined survey data from more than 9,000 people with Myalgic Encephalomyelitis or Chronic Fatigue Syndrome (ME/CFS) across ten European countries.

They found an early onset peak at an average of age 16, and a later one at an average of 37 years old, with seven of the countries showing similar onset peaks individually.

People with early-onset ME/CFS were more likely to report infection as a trigger, be more severely affected and have close relatives with ME/CFS.

The researchers confirmed the presence of two age peaks in a separate group of more than 6,000 people with ME/CFS who took part in DecodeME, a large UK genetics study of the disease.