A recent study by the University of California, San Francisco, has found that stress causes the same changes in cells that are typically caused by aging:
The study involved 39 women ages 20 to 50 who had experienced grinding stress for years because they were caring for a child with a serious chronic illness, and 19 other women with healthy children.
The researchers examined structures inside cells called telomeres - the caps 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 had been caring for a sick child, the shorter her telomeres, the lower her levels of telomerase, and the higher her levels of "oxidative stress," in which so-called 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.
This is very interesting -- it would also help to explain why meditation, yoga, and other activities that reduce stress may have an effect on slowing the aging process.