TIREDNESS is partly genetic - and the people who carry the genes are also more likely to suffer a range of other physical and mental conditions, a study has found.

Research led by Saskia Hagenaars of the Edinburgh University and Vincent Deary of Northumbria University in Newcastle studied the differences in genetics between 111,749 participants who were all asked whether they felt tired or low in energy in the two weeks before their data was collected as part of the UK Biobank study.

The researchers found that genes accounted for around eight per cent of people’s differences in self-reported tiredness, with the majority driven by environmental factors. However, the researchers found that the small genetic contributions to self-reported tiredness overlapped with genetic contributions to a range of mental and physical health conditions, and with whether people smoke, are overweight, and also their longevity.

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The findings, published today in the Springer Nature’s journal Molecular Psychiatry, suggest that it was a person's genetic predisposition to some illnesses - not just presence of these illnesses - that had an association with feeling tired.

This trend was identified participants who were genetically prone to diabetes but who did not actually have the condition, as also in patients with a higher genetic tendency to symptoms of the so-called metabolic syndrome, such as high cholesterol levels, and a high waist to hip ratio or obesity.

A genetic association between tiredness and longevity was also found, and with whether someone had higher genetic tendency to weak grip strength, smoking, depression, and schizophrenia.

Ms Hagenaars said: “Being genetically predisposed to a range of mental and physical health complaints also predisposes people to report that they are more tired or lacking in energy."

Overall, the findings confirm that self-reported tiredness is a partly heritable, complex phenomenon. It has genetic associations with various health, physiological, cognitive, personality, and affective processes, but the researchers stressed that most of people’s differences in tiredness are probably environmental.

Mr Deary added: "There may be a small but significant direct genetic contribution to tiredness proneness."

The research team believes more tests will be done in future to pinpoint links once more genome-wide genotyping data becomes available.