Chronic fatigue syndrome or myalgic encephalomyelitis (CFS/ME) is a common disabling condition characterised by persistent unexplained fatigue that imposes a considerable burden on families and the health services.
Its causes remain unclear, but previous studies have implicated a range of risk factors, including parental illness, childhood psychological distress, academic ability, and high levels of exercise.
The study involved 16,567 babies born in 1970 who were regularly monitored until the age of 30 years.
Risk of lifetime CFS/ME was significantly increased by being female, being in a high social class in childhood, and having a longstanding medical condition in childhood. In contrast, higher levels of exercise in childhood were associated with lower risk.
Other factors, such as maternal psychological disorder, psychological problems in childhood, academic ability, allergic tendencies, birth weight, birth order, and obesity were not associated with risk of later CFS/ME.
"Our findings do not support a role for previously suggested risk factors for CFS/ME," say the authors. "Contrary to previous suggestions that high levels of exercise increase risk, we found that the most sedentary children were at greatest risk, adding further weight to current public health efforts to promote healthy exercise and reduce sedentary behaviour among children."