The thickness of growth marks in primary (or ‘baby’) teeth may help identify children at risk for depression and other mental health disorders later in life, according to a groundbreaking investigation in England.
The University of Bristol team analysed 70 primary teeth collected from 70 children enrolled in the Children of the 90s study (aka the Avon Longitudinal Study of Parents and Children). Parents donated primary teeth (specifically, the pointed teeth on each side of the front of the mouth known as canines) that naturally fell out of the mouths of children aged 5 to 7.
The origin of this study—published in JAMA Network Open—traces back several years to when senior author Erin Dunn learned that anthropologists have long studied the teeth of people from past eras to learn about their lives.
“Teeth create a permanent record of different kinds of life experiences,” Dunn said.
“Exposure to sources of physical stress, such as poor nutrition or disease, can affect the formation of dental enamel and result in pronounced growth lines within teeth, called stress lines, which are similar to the rings in a tree that mark its age.
“Just as the thickness of tree growth rings can vary based on the climate surrounding the tree as it forms, tooth growth lines can also vary based on the environment and experiences a child has in utero and shortly thereafter, the time when teeth are forming. Thicker stress lines are thought to indicate more stressful life conditions.”
Dunn developed a hypothesis that the width of one variety in particular, called the neonatal line (NNL), might serve as an indicator of whether an infant’s mother experienced high levels of psychological stress during pregnancy (when teeth are already forming) and in the early period following birth.
To test this hypothesis, the width of the NNL was measured using microscopes. Mothers completed questionnaires during and shortly after pregnancy that asked about factors known to affect child development.
Several clear patterns emerged. Children whose mothers had lifetime histories of severe depression or other psychiatric problems, as well as mothers who experienced depression or anxiety at 32 weeks of pregnancy, were more likely than other kids to have thicker NNLs. Meanwhile, children of mothers who received significant social support shortly after pregnancy tended to have thinner NNLs.
These trends remained intact after the researchers controlled for other factors that are known to influence NNL width, including iron supplementation during pregnancy, gestational age (the time between conception and birth), and maternal obesity.
No-one is certain what causes the NNL to form, but it’s possible that a mother experiencing anxiety or depression may produce more cortisol, the ‘stress hormone’, which interferes with the cells that create enamel. Systemic inflammation is another candidate.
If the findings of this research can be replicated in a larger study, Dunnn believes that the NNL and other tooth growth marks could be used in the future to identify children who have been exposed to early life adversity.
“Then we can connect those kids to interventions so we can prevent the onset of mental health disorder—and do that as early on in the lifespan as we possibly can.”