Epigenetics refers to the process by which the expression of genes are affected by our internal and external environments, this means that the thoughts and feelings which we experience and also factors such as diet, exercise and social setting will change how our genes express themselves. Genes can either be fully on, fully off, or somewhere in-between (referred to as "dimming"). The consequence of this phenomenon is that it can be manipulated to increase or decrease the phenotype of our genes (how the genes are expressed biologically and physiologically). This means that physical and mental diseases can be changed (treated, prevented or even cured) through our behaviour and environments. While this is quite a new discovery, there are certain drugs which are already being used with epigenetics in mind. Examples of this are seen in drugs improving cholesterol levels and also treating cancer and there plans to treat psycho-pathologies (mental afflictions such as depression / anxiety / schizophrenia) with the same idea in mind.
The idea that I would like to focus on with this post is the behavioural distinction between rats of high nurturing mothers and the rats of low nurturing mothers, as this is how I came across this term.
Within the first week of their life, rats are greatly affected by the nurturing habits of their mothers. This is because immediately after birth, this gene is silenced by methyl molecules. The expression of this gene is determined by the amount of affection the rat receives within its first 7 days of life. High nurturing mothers cause chemical reactions within their rat pups which remove the methyl groups and determine how strongly the glucocorticoid receptor gene is expressed. If this gene remains silenced (as in the case of low-nurturing mothers) then the rat will have a harder time coping with stress. This is because these specific receptor sites are highly involved with the stress response.
When rats (or humans) are stressed, the body releases many chemicals but I'll be focusing on cortisol, because I honestly don't know anything about the others. First of all, the hypothalamus is stimulated by the perceived threat and sends two simultaneous signals, one to the pituitary gland and another along the spinal cord. These two signals are travelling to the same destination however, and this is the adrenal gland. The adrenal gland is where cortisol comes into play. Cortisol gets released into the blood and causes increases in blood pressure, blood sugar and reduces the effectiveness of the immune system (why we tend to get sick more often when stressed out).
There are many effects of the stress response which we all experience such as nervousness, increased energy and increased perspiration. Glucocorticoid receptors in cells will bind with the cortisol and send out calming signals to prevent the stress response from continuing. Rats / humans with lower levels of glucocorticoid receptors will have longer stress responses and can be much more prone to chronic stress than those with higher levels of this receptor.
If you couldn't be bothered reading that then fear not, the jist of it is that high levels of affection near childbirth correlate with a reduced duration of stress following a stressful circumstance.
The effects of this phenomenon can be seen in children and adults who have experienced abuse in their childhood. Methods of reversing these epigenetic changes are being worked on presently. Drugs which remove the methyl molecules from the GR gene within rats have been shown to cause personality trait changes, this makes highly anxious rats become much more calm. This method has yet to be tried out on humans though as it is still being researched but it does look promising. Pretty awesome huh?