Long-term chemical modifications of the gene that regulates the stress response occur in the children of women who experienced severe stress during pregnancy related to partner violence, researchers from Germany observed.
These changes persist into adolescence and may lead to emotional problems and behavioral disorders, emphasize the authors of the study in the Tranlational Psychiatry magazine.
Previous observations show that the severe stress experienced by a pregnant woman may in the future have a detrimental effect on the mental health of her offspring, e.g. it may contribute to behavioral disorders and even to the development of mental illnesses. However, the exact biological mechanisms responsible for the consolidation of the pregnant mother’s experiences in the child’s psyche are not sufficiently understood.
Researchers from the University of Konstanz studied a small group of 25 women and their children, aged 10-19. Mothers lived in Germany, but they had different ethnic origins, for example from Kosovo, Our Country, Turkey, Poland and Iraq.
They were interviewed and asked if they had experienced partner violence before, during or after pregnancy. Physical, sexual and psychological violence was taken into account, because each of them is a source of strong mental stress. 13 women experienced it in at least one of the analyzed periods, of which 8 during pregnancy.
The researchers used blood samples from babies and mothers to assess changes in the gene that encodes the glucocorticoid receptor (GR). This protein is the main regulator of the so-called the pituitary-hypothalamus-adrenal axis, i.e. the biological system that controls growth, reproductive processes, metabolism, behavior, immunity and is involved in the body’s response to stressful situations. Glucocorticoid hormones secreted by the adrenal cortex under stress, such as cortisol, act through GR.
German scientists analyzed the so-called epigenetic changes that chemically modify DNA – for example, by adding a methyl group in a methylation process – but do not affect its sequence. They affect the activity of a given gene.
Previous work has shown that methylation of the GR gene in specific places reduces its activity, which contributes to the dysfunction of the entire pituitary-hypothalamus-adrenal axis. Changes in the functioning of this system may, in turn, lower resistance to stress, lead to depression and other mental disorders, contribute to unfavorable metabolic changes and a decrease in immunity.
It turned out that only the violence experienced by mothers during pregnancy was related to GR gene methylation in children. There was no such modification in the offspring of women whose partner had used violence before or after pregnancy.
However, negative experiences during pregnancy (as well as before and after pregnancy) had no effect on GR gene methylation in mothers – their methylation pattern did not coincide with that observed in the offspring. This means that it was not passed on directly to the child by the mother.
It was also not observed that the methylation of the GR gene was influenced by such factors as, for example, smoking during pregnancy, drinking alcohol or taking drugs, pregnancy complications, the use of painkillers during childbirth, the way of childbirth, the child’s diseases, or its weight after birth.
According to the authors of the study, the obtained results suggest that the intense stress experienced by the pregnant mother may – through changes in the environment of the fetus – lead to long-term methylation of the GR gene in the offspring. In this way, he programs the offspring’s mental vulnerability to stress and negative experiences.
Although these changes were very subtle, they are enough to alter the function of the hypothalamic-pituitary-adrenal axis, the researchers emphasize.
At the same time, they emphasize that their work does not ultimately prove that the relationship between severe stress in pregnancy and methylation of the GR gene is of a cause-and-effect nature.
Although the existence of such a relationship has already been suggested by earlier work. For example, increased methylation of the GR gene has been shown in newborns of mothers who were depressed during pregnancy. These children also showed a stronger hormonal stress response.
According to the scientists, further research is necessary to assess the impact of GR gene methylation on the functioning of the hypothalamic-pituitary-adrenal axis and on the psyche of children.