Unexplained disabling fatigue in childhood is mainly due to genetic inheritance, a study of twins has revealed.
Chronic fatigue in young people can be disabling and is the main illness-related reason for long absences from school.
A genetic study of twins by researchers in Cardiff University's School of Medicine (Department of Psychological Medicine) found that although disabling fatigue and depression occur together, they have different genetic and environmental causes.
Participants were identified from the University's Cardiff Study of All Wales and North West of England twins. Parents of 1,468 twins and 930 older twin pairs took part in the study.
Analysis was undertaken for disabling fatigue of more than one week (short duration) and more than one month (prolonged).
The study led by Dr Tom Fowler with colleagues at Cardiff University and Professor Anne Farmer at the Institute of Psychiatry, London, found that 67% of the influences on short-duration fatigue in children and adolescents are genetic. The results suggest that prolonged fatigue is also linked to familial influences.
Dr Fowler, Department of Psychological Medicine said: "Our research found that the majority of genetic and environmental differences are specific to disabling fatigue and distinct from depression. This suggests the fatigue states in children should be considered as valid entities in their own right, and not as variants of depression."
The research is published in The British Journal of Psychiatry (September edition).
Why study twins?
Twins research at Cardiff University is very important for research into the underlying causes of behaviour. This is because of special features that twins possess. Identical twins come from the same egg and share all of their genes in common.
Non-identical or fraternal twins come from two separate eggs and are no more genetically alike than non-twin brothers or sisters. That is, on average, non-identical twins share half of their genes in common (just as ordinary brothers and sisters do). These natural characteristics are very important for researchers because comparing the similarity of identical and fraternal twins allows us to separate similarity that is due to genes from similarity that is due to environmental influences.
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