Genes may contribute in a small but significant way to why certain people tire easily or suffer from low energy levels.
Being prone to tiredness is partly heritable, according to researchers, with genetics accounting for eight per cent of differences between people who were asked about their levels of tiredness.
The large-scale study was led by Saskia Hagenaars, a PhD student at the University of Edinburgh's Centre for Cognitive Ageing and Cognitive Epidemiology and Dr Vincent Deary of Northumbria University.
They analyzed genetic make-up from 111,749 participants who had reported whether they whether they had felt tired or had low energy in the two weeks before data was collected for the UK Biobank.
Researchers also found that the genetic predisposition to tiredness was often present in people genetically prone to a range of mental and physical health conditions, such as smoking, depression and schizophrenia.
A genetic overlap was also identified between low energy levels, and high cholesterol levels and obesity.
According to the researchers, this raises the possibility of a genetic link between tiredness and a vulnerability to physiological stress.
In general, the genetic overlap was found to exist between tiredness and a general tendency to poor health.
Most of people’s differences in tiredness are probably environmental, the researchers say. The genetic data accounted for only 8.4 percent of people’s differences in tiredness.
The findings are published in a paper, Genetic contributions to self-reported tiredness, in the journal Molecular Psychiatry.
Some people report feeling generally more wabbit or puggled than others. Our results suggest that a small but detectable part of that variation is related to differences in people's genes. And the genes involved are associated with a range of health and personality factors.