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BRISTOL, UK/BOSTON, US: The thickness of growth marks in primary teeth may help identify children at risk for depression and other mental health disorders later in life, according to a study led by researchers at Massachusetts General Hospital (MGH) in Boston using data from a health study conducted in Bristol. The study results may help in developing a tool for identifying children who have been exposed to difficulties early in life—a risk factor for psychological illness—offering support and preventive treatments if necessary.
According to previous studies, children’s exposure to prenatal and perinatal maternal psychosocial distress can have an impact on their brain health across the life course. Not only does the mother’s psychosocial stress almost double the risk of a mental disorder, but also it can become biologically embedded in children and lead to lifelong physiological and neurobiological disorders.
Although a better understanding of risk factors is needed, data such as prenatal medical records are often unavailable, resulting in studies having to rely on retrospective—and subjective—maternal self-reports. Thus, researchers were in need of novel and objective measuring instruments and assumed that primary teeth would be suitable, as the exposure to sources of physical stress, such as poor nutrition or disease, can affect the formation of dental enamel, resulting in pronounced growth lines. These lines may vary, based on the environment and experiences of the child before birth and shortly after; thicker lines indicate elevated stressful life conditions.
“Teeth create a permanent record of different kinds of life experiences,” said senior study author Dr Erin C. Dunn, who is from the Psychiatric and Neurodevelopmental Genetics Unit at the Center for Genomic Medicine at MGH and also an associate professor in the Department of Psychiatry at Harvard Medical School, in a press release.
The research team hypothesised that the width of a particular line—the neonatal line—could serve as an indicator of whether the child’s mother had been exposed to high levels of psychological stress during pregnancy and the early period following birth.
“Teeth create a permanent record of different kinds of life experiences”
— Dr Erin C. Dunn, MGH
To test their hypothesis, the researchers used microscopes to analyse 70 exfoliated primary canine teeth collected from 70 children aged 5 to 7 enrolled in the Avon Longitudinal Study of Parents and Children based at the University of Bristol. In addition, the mothers completed questionnaires that investigated four factors that are known to affect child development: stressful events in the prenatal period, maternal history of psychological problems, neighbourhood quality and level of social support.
It was found that children whose mothers had suffered from severe depression or other psychiatric problems throughout their lives, as well as children whose mothers had experienced depression or anxiety at 32 weeks of pregnancy, were more likely to have thicker neonatal lines than other children. In contrast, children of mothers who had received a great deal of social support shortly after pregnancy were more likely to show thinner neonatal lines. These results were maintained, even after the research team took other factors that are known to influence neonatal lines into account.
According to Dr Dunn, up until now it has not been clarified what influences the formation of the neonatal line. One possible explanation is that mothers who experience anxiety or depression produce higher amounts of cortisol, interfering with the cells responsible for enamel creation. Another explanation could be systemic inflammation, she added. Dr Dunn believes that, if the present research findings can be replicated in a larger study, the neonatal line and other tooth grow markers may be used in the future to identify children who have been exposed to early life adversity. She said: “Then we can connect those kids to interventions so we can prevent the onset of mental health disorders, and do that as early on in the lifespan as we possibly can.”
The study, titled “Association of maternal stress and social support during pregnancy with growth marks in children’s primary tooth enamel”, was published in the November 2021 issue of JAMA Network Open.