Chronic stress appears to accelerate the withering of the tips of the bundles of genes inside cells, shortening their lifespan and speeding the body's deterioration, according to the study published in the Proceedings of the National Academy of Sciences.

If the findings are confirmed, they could provide the first explanation on a cellular level for the association between psychological stress and increased risk of physical disease, as well as the perception that unrelenting emotional pressure accelerates the aging process.

We all know that stress seems to age people ­ just look at the aging of our presidents after four years, said Dennis Novack, who studies the emotions-health link at Drexel University School of Medicine in Philadelphia. The new study demonstrated that there is no such thing as a separation of mind and body ­ the very mollecules in our bodies are responsive to our psychological environment.

The researchers examined the structures inside cells called TELOMERES the tips located at the ends of chromosomes. Every time a cell divides, telomeres get shorter. In the natural aging process, the telomeres eventually get so short that cells can no longer divide, and they die.

The researchers also measured levels of an enzyme called TELOMERASE, which helps rebuild telomeres to stave off this process. Telomerase levels naturally decline with age.

The researchers found that the longer a woman has been caring for a sick child, the shorter her telomerase, the lower her levels of telomeres, and the higher her levels of oxidative stress, in which free radicals in the body damage DNA, including telomeres.

Compared to women with the lowest levels of perceived stress, women with the highest perceived stress had telomeres equivalent to someone 10 years older, the researchers found.