British scientists analyzed the structure of the enamel of milk teeth in 70 children. The analysis showed which children may have been exposed to stress hormones in the prenatal age. Thanks to their observations, researchers hope to detect possible mental disorders and depression in humans faster.
The width of the line in the enamel of deciduous teeth can help identify children at risk of depression and other mental disorders in adulthood, according to a groundbreaking study in the academic journal JAMA Network Open.
The grooves on the tooth surface
The outermost layer of the tooth is enamel. However, it is not a fully smooth structure – it has characteristic lines (grooves, friezes) reflecting the deposition of successive layers of enamel during tooth growth. These lines can be shallower or deeper, narrower or wider.
A team of researchers from the University of Bristol analyzed 70 deciduous teeth collected from 70 children participating in the Children of the 90s study (also known as the Avon Longitudinal Study of Parents and Children). The teeth (mostly canine teeth) were provided by the parents after they dropped out naturally to toddlers between the ages of five and seven.
In-depth analysis has shown that the enamel structure of these mammals, especially the width of one of the grooves on its surface – the so-called neonatal line (NNL), may be related to prenatal and perinatal life experiences. This discovery, according to the authors, lays the groundwork for the development of a much-needed tool to identify children who were exposed to severe adversity early in life, which is a risk factor for the development of psychological problems. Such a tool would enable the monitoring of the fate of children at risk and the implementation of appropriate prophylaxis that would prevent the occurrence of mental disorders for many years before their first symptoms appear.
Teeth – a record of life experiences
The genesis of this research goes back a few years, when its older author, Dr. Erin Dunn, stumbled upon a work in the field of anthropology with its own long-standing research problem. Dunn is a social and psychiatric epidemiologist who studies the effects of early childhood adversity. They are one of the most important risk factors for the development of mental health problems, and according to research, they account for up to a third of all psychiatric disorders.
Dr. Dunn is particularly interested in whether there is a point in a child’s development where he or she is particularly sensitive to these adverse events. This is difficult because so far scientists have not had the tools to measure exposure to childhood adversity. Asking the patients themselves (or their parents) about painful experiences from their childhood is the only method, and also quite unreliable, because it depends on not always good memory or reluctance to share difficult memories.
One day, however, Dr. Dunn read that anthropologists had long examined the teeth of people from bygone eras to learn more about their lives.
– I learned that teeth create a permanent record of various types of life experiences – says the researcher.
For example, exposure to sources of physical stress, such as poor nutrition or disease, can affect enamel formation and cause more pronounced growth lines on the teeth. These lines are called stress lines. They are similar to tree rings in wood, says Dunn.
– As the thickness of the rings may vary depending on the climate surrounding the tree during its formation, the lines of tooth growth may differ depending on the environment and the child’s experiences in the prenatal period and immediately afterwards, i.e. when the teeth were forming – she explained . “Wider lines on the enamel are believed to indicate more stressful living conditions,” he adds.
Dunn therefore hypothesized that the width of the line, especially one called the neonatal line (NNL), could serve as an indicator of whether the infant’s mother experienced high levels of mental stress during pregnancy and just after the baby was born.
Tooth observations and questionnaires
To test her theory, she and two co-workers measured the deciduous teeth provided by parents while asking mothers to complete questionnaires about their life and mental well-being around the time of birth. They asked about four factors known to affect a child’s development: stressful events in the prenatal period, the mother’s history of psychological problems, the quality of the living conditions (for example, did the mother live in poverty, did she feel safe where she lived) and for the level of social support.
The analysis revealed several clear patterns: babies whose mothers had severe depression or other psychiatric problems throughout their lives, and babies of mothers who experienced depression or anxiety at 32 weeks gestation, more often than other babies, with coarser NNL. Meanwhile, the children of women who received significant social support shortly after pregnancy tended to have clearly thinner NNLs.
These trends did not change even after taking into account other factors that could affect NNL lines, including iron supplementation during pregnancy, gestational age (time between conception and birth), and maternal obesity.
“No one is sure what determines NNL width,” Dunn says, “but it’s possible that a mother experiencing anxiety or depression produces more cortisol, the so-called stress hormone, and that it interferes with the cells that make up the enamel. Another explanation may be the systemic inflammation in the mother’s body, she says.
The researcher hopes to clarify this soon. At the same time, she emphasizes that the results of her research to date can be used in the future to identify children who were exposed to adversities early in life.
– And in such children we can implement appropriate interventions that will prevent the occurrence of mental health disorders as early as possible – he concludes.
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