Mother's stress changes the son's genes

For decades we have heard that children are like sponges. Now science shows that this statement is true. But this enormous capacity to adapt to the environment is a double-edged sword. In the early years of life neurons have an enormous plasticity, which means that the brain can develop a great potential or, on the contrary, can undergo a damage difficult to repair. And parents have a crucial role to tilt the balance in one direction or another.

The relationship that parents establish with the child, their ability to satisfy his emotional needs and also his state of mind during the early years, influence the psychological development of the small boy and leave a deep mark that probably will accompany him throughout life.

In fact, several studies have linked maternal depression with the onset of mental disorders in children. It is also known that when parents have marital problems and often argue, their children become emotionally insecure and have difficulty establishing healthy relationships in adulthood. In addition, it is also seen that when parents are subject to high stress is more likely that children develop an emotional problem.

Now, a new study conducted at the University of Wisconsin revealed that problems are not limited to psychological level, the parental stress may also alter the genetics of their children by making sure that in their brain will be forming connections that will eventually affect their reaction to adversity.

In fact, it is the first time that scientists find a link between parental stress and DNA of children. This study shows that parents, and our experiences in general, may affect our genetics.

The stress response is partly determined by genes

The idea that stress can damage DNA and brain development comes from a study conducted in 2004 at McGill University. These researchers worked with mice and found that when mothers cared carefully their sons it was activated a gene in their brain that triggered a mechanism through which young mice developed increased tolerance to stress, they were able to better adapt to changes, showed less fear and were more likely to explore their environment.

Subsequently, a study of the Douglas Mental Health University Institute made with human, revealed that child abuse and parental neglect can also mute the receptors of stress hormones in the brain. It was noted that in children who had suffered abuse in childhood and who later committed suicide, the gene that had to activate the receptors of stress hormones remained inactive.

The problem is when this gene is silenced, the response to stress natural system does not work properly, so it is more difficult to address the problems and adversity, and these people are more likely to develop psychological disorders and commit suicide.

In fact, another study conducted at the University of British Columbia found that when mothers are depressed or anxious, the gene responsible for receptor activation of stress hormones tended to be inactive in infants. As a result these children are more fearful, they find it difficult to adapt to changes and will have problems to deal with stressful situations.

Stressed mothers, children less resilient

This new study reveals that to experience some changes at the DNA level is not necessary that children suffer physical abuse. These researchers analyzed hundreds of parents for more than a decade. Parents completed a series of questionnaires at different times during the life of their children when they were infants, 3 and 4 years of age and later, upon reaching adolescence. Through questionnaires, the researchers assessed the level of parental stress. After they had reached the age of 15 years, the scientists analyzed the DNA of these 109 adolescents.

Thus they found differences in the DNA of young people whose parents had shown greater levels of stress. It was also noted that the stress of both parents did not affect in the same way. In fact, a high level of stress in mothers during the first years of children's lives was related with alterations in 139 genes. Fathers’ stress accounted less, although it could be related to changes in 31 genes. This difference may be due to the fact that many fathers are less involved in raising children, so it is likely that the impact of their emotional state is minor.

Another important finding indicates that stress of mothers and fathers does not cause significant changes in the expression of genes when took place after 3 years of age. This could be due to the fact that the first three years of life are the phase of maximum plasticity of the brain, when the brain regions are able to adapt more and also assume the functions of other sectors if the subject suffer any brain damage. From this age, the brain continues to change, but it does so at a slower pace.

Among the altered genes (normally silenced) by stress have been met two which are particularly important for brain development and behavior as they are related to cellular communication and the membranes of neurons. One of the genes involved is the Neurog1, which stimulates the growth of new neurons, which is crucial for growth, learning and memory.

Researchers explain that these changes in the expression of DNA affect the way in which neural connections are established, and then, the functioning of the brain. In practice, silencing the gene responsible for receptor activation of stress hormones, the child will not have the necessary tools to neruological level to cope with difficult situations. If there are not enough receptors for hormones such as cortisol and adrenaline, they remain active, causing damage to the body, while the brain is unable to find an appropriate solution. Therefore, it is likely that the child will be more irritable, impulsive and fearful.

However, it should be clear that our brain has an amazing plasticity, so despite changes in gene expression it does not mean that these children can not learn to manage stress assertively developing a more resistant attitude when they reach adolescence or adulthood, but it will be more difficult.

In any case, the message for parents is clear: stress is harmful not only for adults but also for children, especially if they are very small.


Sources:
Essex, M. J. et. Al. (2013) Epigenetic Vestiges of Early Developmental Adversity: Childhood Stress Exposure and DNA Methylation in Adolescence. Child Development; 84(1): 58-75.
McGowan, P. O. et. Al. (2009) Epigenetic regulation of the glucocorticoid receptor in human brain associates with childhood abuse. Nature Neuroscience; 12: 342-348.
Oberlander, T. F. et. Al. (2008) Prenatal exposure to maternal depression, neonatal methylation of human glucocorticoid receptor gene (NR3C1) and infant cortisol stress responses. Epigenetics; 3(2): 97-106.
Preston, S. L. & Scaramella, L. V. (2006) Implications of timing of maternal depressive symptoms for early cognitive and language development. Clin Child Fam Psychol Rev; 9(1): 65-83.
Weaver, I. C. (2004) Epigenetic programming by maternal behavior. Nature Neuroscience; 7(8): 847-854.
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