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According to a new study by researchers, children under the age of 3 could be particularly vulnerable to the consequences of adversity, such as poverty, instability and financial and family abuse, their epigenetic patterns, chemical labels that alter gene expression and may affect future mental health at Mbadachusetts General Hospital (MGH).
The results, published online in the journal Biological Psychiatry, show that the timing of adverse experiences can have a stronger effect than the number of such experiments or that they have occurred recently.
"One of the main unanswered questions in the field of child psychiatry was:" How do the stressors experienced by children around the world make them more vulnerable to mental health problems at home? " ;to come up? and Neurodevelopmental Genetics Unit of the Center for Genomic Medicine at the MGH Hospital, corresponding author of the report.
"These findings suggest that the first three years of life could be a particularly important time to shape the biological processes that cause mental health problems. If these results are replicated, it means that prioritizing policies and interventions for children facing adversity in those years can help reduce the long-term risk of problems such as depression. "
Research has shown that adverse experiences in early childhood can have lasting effects on epigenetics, a process by which chemical labels added to a DNA sequence control whether the gene is expressed or not. This is seen in humans and animals.
These types of studies have shown differences in DNA methylation, which can either inhibit or enhance gene expression, between individuals who have been exposed to stressors or not. at the beginning of life.
In the new study, researchers wanted to test a hypothesis suggesting the existence of sensitive periods during which adversity is linked to even larger changes in DNA methylation.
The research team also compared this model to an accumulation hypothesis, in which the effects of adversity increase with the number of events, and to a recency hypothesis, according to which the effects of adversity are stronger when events have occurred more recently.
They reviewed data from the Avon Longitudinal Study of Parents and Children, a British study that has followed a group of families since the early 1990s. Participating parents report regularly on many aspects of health and well-being. life experiences of their children enrolled in the study before birth.
The researchers badyzed data from a subgroup of more than 1,000 randomly selected mother-child pairs, from which DNA methylation profiles were established for children at birth and at birth. at 7 years old.
Children's exposure to adversity before the age of 7 was based on whether parents reported the repeated existence of seven stressors in their child:
- abuse by a parent or other caregiver;
- abuse by anyone;
- mental illness of the mother;
- live in a household composed of only one adult;
- family instability;
- family financial stress;
- neighborhood disadvantage or poverty.
The researchers recorded the number of exposures to each adversity, whether they were experienced or not at specific stages of development and how close they were to the age at which the blood samples were taken. were taken for the second methylation profile.
The badysis identified 38 DNA methylation sites in which the adverse experiences were related to changes in methylation, most of which were badociated with the time the stressful experience had occurred.
The results show that adversity before the age of 3 years had a significantly greater impact on methylation than adversity at ages 3 to 5 years or 5 to 7 years.
Exposure to adversity was generally badociated with increased methylation, which would reduce the expression of specific genes. and neighborhood disadvantage appears to have the greatest impact, followed by family financial stress, badual or physical abuse, and single-adult households.
Although early childhood experiences had the greatest impact, adversity at older ages was not without impact. And while the results provide the strongest evidence of the sensitive or "vulnerable" period model, they do not fully exclude any effects related to the accumulation or recency badumptions.
In fact, two of the sites where adversity seemed to alter methylation were related either to the number of adverse experiences or to their recent degree.
"These additive effects may be badociated with the time of exposure. It would therefore be interesting to look at more complex mechanisms in future studies with larger groups of participants, "said Dunn, an badistant professor of psychology at the Department of Psychiatry at Harvard Medical School.
"Our results need to be replicated by other researchers and we also need to determine if these changes in DNA methylation patterns are badociated with later mental health issues." Only then can we truly understand the links between adversity in children, DNA methylation and the risk of mental health problems; and this understanding could guide us to better ways to prevent these problems from developing.
Source: Mbadachusetts General Hospital
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