from THE INDEPENDANT
Thursday, December 2 2010
Stressed out? It could be in your genes.
By Laura Spinney
A growing body of scientific evidence suggests that not only can stress bring about permanent changes in your body, but you can even pass on some of those changes to your offspring.
Rachel Yehuda, a neuroscientist at the Mount Sinai School of Medicine in New York City, had her first inkling of the indelible mark that stress can leave on families back in 1993, when she opened a clinic to treat the psychological problems of Holocaust survivors, and was deluged with calls from their adult children. Investigating further, she found that those children were particularly prone to post-traumatic stress disorder. Both parents and children tended to have low levels of the hormone cortisol in their urine. Stranger still, the more severe the Holocaust survivors’s PTSD symptoms, the less cortisol there was in their child’s urine.
Cortisol plays an important role in the body’s stress response. When a threat presents itself, the brain instructs the adrenal glands……to release hormones, including adrenalin, into the blood. When the threat has passed, the brain sends another signal to the adrenal glands to release cortisol. Cortisol shuts down the stress response by binding to receptors in certain regions of the brain, including the hippocampus.
At McGill University, in Montreal, Canada, neuroscientist Michael Meaney has shown that stressful events in the early lives of rats, such as being reared by a negligent mother, can affect their response to stress as adults. The pups of negligent mothers grow up to be fearful and skittish, and they have fewer hippocampal receptors to corticosterone (the rat equivalent of cortisol) than pups of attentive mothers.
Last year, Meaney’s group made headlines when it reported a similar finding in humans. Meaney’s former student Patrick McGowan managed to get hold of tissue samples from the brains of 24 adults who had committed suicide, half of whom had been abused as children, and half of whom had not. The researchers found that the hippocampi of the abuse victims contained fewer cortisol receptors than those of the individuals who had not been abused.
In both rats and humans, therefore, stressful early life events leave an enduring trace in the brain, causing those brains to be less sensitive to the stress-dampening effects of cortisol. And in both speices, the reduced sensitivity is associated with so-called epigenetic changes – chemical modifications to DNA that alter the activity of genes without altering the genes themselves. Genetic change, also known as evolution, takes millions of years, but epigenetic changes can be accumulated in a lifetime, allowing organisms to adapt more quickly than their genomes can.
Meaney’s group found that the gene encoding the corticosterone receptor in rats carries different epigenetic marks, or modifications, in the brains of the offspring of negligent and attentive mothers. As a result, the gene is less active in the neglected offspring, meaning that it is translated into fewer of those critical receptors – the ones responsible for shutting down the stress response – with profound consequences for the pups’ behavior. They found a similar difference between the abused and the non-abused suicide victims.
Yehuda began to wonder if epigenetic mechanisms could explain the vulnerability to PTSD of the children of Holocaust survivors. Most epigenetic marks are erased during the formation of the gametes – the sperm and egg – so that each generation starts out a blank slate. However, there is now good evidence that some survive that erasure process, and stress-related marks are among them.
(this is just part of this article)
I have always suspected this. However, I thought that PTSD would be passed on through behavior or emotion or attitude. I never suspected it could be passed on genetically. I guess, though, since the psyche is subtle, it is bound to express itself in the physical world, somewhere.
Dynamics of the nature described above must come into play a lot at this time of year, especially after a couple of drinks all around. “A Course in Miracles” states that “The past is not real.” So, as an adult, one could think that way and only deal with family ‘here and now’, all memories deleted, at least for one Christmas celebration.
Have a cortisol filled Christmas.