But what if both good and bad parenting styles leave marks on the child, and in particular their DNA?
Our Genetic Code
When we are born we inherit our genetic code from our parents. Half our DNA is from our mother and half from our father, and the same code is found in each and every cell in our bodies. It has long been established that DNA is stable over an individual’s lifetime; the sequence does not change.
However, this creates a number of questions. Firstly, if every cell in the body contains the same code, why don’t all the cells in our bodies do the same job? Or, how does a brain cell know it’s a brain cell and not a skin cell if they both have the same code? Secondly, it also begs the question; why are people who are genetically identical very similar but not exactly the same? And finally, (in terms of this post but by no means in the grand scheme of things) why do certain psychological disorders seem to run in families but are not 100% heritable?
For most people the last two questions can be answered in terms of “the environment”, or nurture, in the age-old debate. But for a molecular biologist, or geneticist that is not an answer. They want to understand at the cellular level, and the answer it appears lies in something known as epigenetics.
Epigenetics refers to changes in the expression of genes, and these genes code for proteins. Therefore, epigenetic changes to DNA will affect (normally reduce) the amount that a gene is transcribed and therefore, reduce the amount of protein produced by a cell. The DNA itself remains unchanged.
The Epigenetics of Parenting Style.
Back in 2004 a group of researchers decided to look at the parenting style of rats, dividing them broadly into two groups; one group with those that gave high levels of care to their off-spring, and another group with those who gave low levels. They found that the offspring of the high maternal care group appeared to cope better with stress than offspring of the low maternal care group.
Genetic analysis showed epigenetic differences in the high and low maternal care group. These changes coded for a particular protein involved in the stress response: a glucocorticoid receptor, found in the hippocampus. It appeared that these changes meant that the high maternal care group had more glucocorticoid receptors than those in the low maternal care group, something that could help to account for the differences seen in the stress response of the two groups. Interestingly, these changes appeared not to be permanent as the group found that these epigenetic changes could be reversed within the first few weeks of life if the rats were “fostered” by mothers from the alternative group.
Since then the search has widened to look at other proteins and brain areas which might be altered epigenetically by early life experience. Together, these may help to explain at a biological level, the connection between early experience and the development of later psychological pathologies such as addiction or depression.
More recently, experiments are underway to look at the heritability of these epigenetic changes. The idea that we might be able to pass on epigenetic changes to our children has been studied more widely when looking at familial cases of cancer, which is unconnected to parenting style I hasten to add! Now, scientists are interested in looking at the possibility that we might be able to pass on early experience induced epigenetic changes to our children. This idea might help us to understand better the apparent familial links of some psychological disorders.
So what does this mean for parenting guides? Well, probably not a lot. Most of these studies involve the offspring in extended periods of isolation from their caregivers, something which is unlikely to happen by accident, but does occur in more extreme cases of neglect and abuse. Studies also show that we all acquire these epigenetic changes throughout our lives and this may explain why that explains why identical twins are not completely identical.
Therefore, as Dr. Chris Murgatroyd pointed out at the BNA2013 Neuroscience conference, perhaps we should not see epigenetic changes as necessarily unhelpful, but rather something that allows us to adapt to our environment. For example, if we grow up in a very stressful environment, our bodies need to be able to adapt to these higher levels of stress. However, the problem comes when our circumstances change and our epigenetic markers do not. This can create an mismatch between the stimulus and our response to it because the quantities of different hormones we are producing are adapted to deal with a different environment.
For these and many other reasons, it is important not to over emphasise the results of these studies. Epigenetics will not fundamentally alter what we know about genetics, nor will it have much affect on how the majority of people bring up their children. But it might help us to improve the bridge between biological and psychological sciences, so that we gain a deeper understanding psychological phenomena. This in turn will help improve treatment options, be they pharmaceutical or psychological, for many frequently occurring and debilitating conditions.