Men who remain jobless for more than two years show signs of faster genetic ageing, research has shown.
Scientists made the discovery after examining a genetic marker of biological ageing in DNA samples from 5,620 Finnish men and women.
They focused on telomeres, caps on the ends of chromosomes that perform a similar role to the plastic ends of shoelaces, by preventing DNA becoming frayed and degraded.
Telomeres shorten as cells divide, eventually ceasing to function. They shorten at different rates over the lifetimes of different individuals, and short telomeres are linked to age-related conditions such as type 2 diabetes and heart disease.
The British and Finnish scientists looked at telomere length in blood cell samples collected in 1997, when all the participants were 31 years old.
Men who had been unemployed for more than two of the preceding three years were more than twice as likely to have short telomeres as men who were continuously employed.
The trend was not seen in women, but fewer women than men in the study had been unemployed for long periods in their 30s.
Co-author Dr Leena Ala-Mursula, from the University of Oulu in Finland, said: "There has been lots of research linking long-term unemployment with ill health. This is the first study to show this type of effect at a cellular level. These findings raise concerns about the long-term effects of joblessness in early adulthood. Keeping people in work should be an essential part of general health promotion."
The scientists accounted for social, biological and behavioural factors that could have affected the result. This helped to rule out the possibility that short telomeres were linked to medical conditions that prevented men from working.