Scientists have known for some time that the effects of stress can be passed down through generations (See: Stress and Poverty definitely not good for you) but didn’t understand exactly how.
Researchers now believe they have solved the puzzle. Stress is thought to cause epigenetic changes to genes which don’t actually alter the DNA sequence but leave marks that influence how active genes are.
So if mice are stressed for two weeks after birth their offspring will show signs of depression and anxiety despite enjoying maternal care. There is now evidence that health problems such as diabetes, obesity, and mental illness could be the results of stress on parents and even grandparents.
Scientists in Japan have found that chemical or environmental stress detaches a protein from chromatin the DNA that makes chromosomes. This particular protein keeps the chromatin zipped up but once detached it effectively unzips the chromatin activating genes that would normally be hidden.
The critical point is that the unzipped chromatin is inherited by all descendants of the original stressed cell. If that cell is a sperm or an egg it ends up in every cell in any offspring.
In experiments with stressed fruit flies the changes passed only to the next generation if they mated with a healthy flies but passed to the next 3 generations if both flies had been affected by stress.
Mammals have a similar protein and the same changes have been seen in mice. So now there is a clear mechanism at molecular level that responds to stress and the implications may be useful in cancer therapy.
Source: New Scientist 2 July 2011
Despite the reported increase in stress levels (See: Stress back on the agenda) we also now know that we are not necessarily at the mercy of our genes or our environment, and that our own efforts can make a difference (See: Practise makes Perfect)