The emerging field of behavioural epigenetics is starting to make its mark in the ‘applied’ fields of clinical psychology and behavioural medicine. And here’s the reason why.
It will probably come as no surprise to discover that your behavioural style (personality, if you will) is, in large measure, genetically inherited from your parents. But, and here’s where it gets interesting for mental health clinicians, it seems that the genetic inheritance you were dealt may, at least in its behavioural expression, be highly malleable.
A little background here: For most of the time since DNA was discovered – it was first isolated by Swiss biological chemist Friedrich Miescher in 1869, who called his discovery ‘nuclein’ – mainstream scientists have viewed an individual’s DNA as a biological constant. In other words, the DNA you inherited at birth would remain unchanged throughout your lifespan, unless you’d suffered exposure to known DNA ‘corruptors’ such as radiation.
Then, in the 1980s, papers began to appear challenging this orthodoxy. Israeli biochemist, Dr Aharon Razin, is a notable name in this regard. In a series of publications, he reported how, in response to a number of biochemical factors, the body would attach methyl or acetyl groups to our DNA, changing its physical structure and hence its function. How exactly? Well, Methyl groups cause DNA to coil-up and become less accessible for transcription (copying) – leading to reduced gene expression. Acetyl groups, on the other hand, have the opposite effect; loosening the DNA coil, increasing the ease of copying and so promoting gene expression. What is more, it appeared as though such changes were permanent, at least until such time as future biochemical influencers prompted further change.
Groundbreaking as these discoveries were, the “biochemical” factors responsible for Dr Rizvin’s observation were physical and, generally speaking, considered to be outside of conscious control. So, our understanding of DNA had been given a good shaking; perhaps it wasn’t quite as static as we first thought, but we hadn’t quite reached a paradigm-busting point in our understanding.
Cue, stage left…. Dr Ian Weaver and collaborators (including noted biologists Moshe Szyf and Michael Meaney), who reported that DNA expression was, in fact, so pliable that even (!) behaviour could cause it to change.
In their experiment, (Epigenetic programming by maternal behavior; Weave Ian C G et al.; Nature Neuroscience 7, 847 – 854 (2004)) two groups of rat pups were raised by mothers who were either nurturing or neglectful. The results showed that in the neglected pups, hippocampal DNA was highly methylated, and this stood in contrast to the virtually complete absence of methylation in the nurtured pups. The reduction in transcription caused by the high levels of methylation meant that the neglected pups formed fewer glucocorticoid receptors in the hippocampus (crucial to stress management). It is posited that this was a major contributory factor to the neglected group being more socially withdrawn and less calm than their more fortunate lab-fellows. The authors concluded that this showed “that an epigenomic state of a gene can be established through behavioral programming, and it is potentially reversible.”
Subsequent work, by Dr Eric Nestler, has also indicated that such behaviourally induced epigenetic shifts are not restricted to the formative years but can occur in adulthood too. And, perhaps more surprisingly, it seems that they can also be passed down to the next generation.
Nestler, who is Nash Family Professor of Neuroscience at Mount Sinai school of medicine, New York, reported one study in which the off-spring of a group of bullied male mice where found to be hypersensitive to stress, despite never having had any contact with their bullied fathers. He noted that: ‘It was not a subtle effect; the offspring were dramatically more susceptible to developing signs of depression.”
To maintain our perspective, Nestler has expressed some caution about how far such transgenerational transmission might occur. In a 2012 interview with Sandra Aamodt, from BeingHuman.org (published 11/06/2012 ), Nestler noted that: “Other labs have taken that result out several generations. But when we harvested the sperm from the stressed mice and impregnated another group of normal females through in vitro fertilization, the offspring of those mice largely lacked any difference in stress responses.” Nestler continued: “There are caveats, and we need to do more difficult experiments, but those are the kinds of things that we’re thinking of.” “But, he concludes “I think epigenetics is going to be huge. It explains how the environment interacts with the genome to produce a response or an adaptation.”
So, it would seem that behavioural epigenetics is here to stay, but where’s the evidence for all of this applying to humans?
Well, lets close by refering to just one paper, that is illustrative of the expanding body of work supporting the validity of the behavioural epigenetic paradigm in people too.
Published in the open-access journal PLOS One (Manoj K. Bhasin, Jeffery A. Dusek, Bei-Hung Chang, et al, May 2013), researchers from the Benson-Henry Institute for Mind Body Medicine, Massachusetts and Beth Israel Deaconess Medical Centre at Harvard, trained 26 adult participants in various relaxation techniques and blood tests enabled the analysis of 22,000 different gene sequences.
The results showed that relaxation practice enhanced expression of genes associated with energy metabolism, mitochondrial function, insulin secretion and telomere maintenance, and reduced expression of genes linked to inflammatory response and stress-related pathways.
In the authors own words, they conclude that their findings : “for the first time [in human subjects] indicate that relaxation response elicitation, particularly after long-term practice… mitigates stress.” Nuff said?
And the take-away message of all this?
Well, it’s virtually certain that we’re only at the beginning of our behavioural epigenetics expedition; so keep watching this space but, above all, keep relaxed… and give yourself some control over the course of your own future journey.