Interview: “Have we been ignoring teeth?”
Dr. Erin C. Dunn, Assistant Professor of Psychology at Harvard Medical School, Boston, U.S., is a scientist working to identify strategies to prevent mental health problems, particularly among children, adolescents and young adults. According to Dunn, mental health problems, including depression and anxiety, affect one in five people worldwide. At the recent American Association for the Advancement of Science (AAAS) Annual Meeting, which took place from Feb. 14 to 17 in Washington, Dunn and her research team had the opportunity to talk about a promising, yet highly understudied, biomarker for contemporary medicine: teeth. In their study, the researchers found a correlation between markers of tooth development, such as enamel and dentin formation, and risk of mental health symptoms.
Dr. Dunn, how did you become interested in this research area?
As a scientific community, we have spent decades trying to find ways to identify people, especially children, who are at risk of developing a mental health problem. One of the things we study in our research group is the role that stress and exposure to childhood adversity have in shaping these short- and long-term mental health risks. We examine the effects of experiencing multiple types of adversities while growing up, including being poor, experiencing abuse or neglect, or having a parent with mental health problems. From our own research and others’ work, we know that early life adversity is one of the strongest risk factors for having mental health problems and at least doubles the risk of having a mental health condition. This is a very strong and consistent finding across multiple research studies.
However, what is less clear is whether the age when children are exposed to adversity matters. In other words, are there certain age stages when being exposed to childhood adversity is even more harmful? To answer this question, we have been working to discover what scientists call “sensitive periods” in development. Sensitive periods can be thought of as windows of vulnerability during the life span, when the brain is especially sensitive to life experiences. We believe that life experiences, including exposure to childhood adversity, during these sensitive periods can have lasting impacts on brain health. Nevertheless, they can also be seen as windows of opportunity, where health-promoting interventions may be most effective.
A major challenge in studying sensitive periods is that there is no consistent way of capturing adversity exposure because all of our current measures have serious limitations. For example, it is often hard for people to recall whether they experienced certain adverse events and, if they did, how old they were when this happened. We realized that if we wanted to better understand the relationship between adversity exposure and future mental health risk, we needed to come up with better ways of capturing exposure to adversity that did not rely on people’s self-reports.
Why do teeth represent a promising source of information in this respect?
Ideally, this new measure of exposure to adversity would be a biological marker, or biomarker, that can be routinely used to measure both stress exposure and people’s risk of having mental health problems in the future. This biomarker would be noninvasive to collect, reliable, valid and inexpensive. Over the past few years, our research has been interested in teeth as being one such biomarker. We think that teeth show promise in this area. They develop incrementally in layers, like rings in a tree, and potentially record information about the timing of various early life exposures. They also begin developing in utero (in the case of deciduous dentition) and continue forming through adolescence (in the case of permanent dentition), providing a window into multiple sensitive periods of development in the first two decades of life. Therefore, we see an exciting opportunity to explore teeth as potential biomarkers to help us better understand this risk of future mental health problems.
What methods of data collection and analysis were used, and what are the key findings of the study?
In our AAAS session, we presented results of a substudy conducted among a sample of 37 children who were kindergarteners (age 6); this substudy is part of a larger study based in California that followed children for several years and is called the Peers and Wellness Study (PAWS). When enrolled children began losing their primary dentition––specifically, their deciduous incisors––PAWS researchers asked parents to donate these teeth to the substudy. At the same time, parents and teachers were asked to rate the children’s level of mental health problems using a set of questionnaires that asked about different emotional and behavior problems.
We performed high-resolution imaging of those teeth and were able to identify a set of measures to characterize them in terms of the thickness of the enamel and the volume of the tooth pulp, among other factors. We found an association between some of these measures and children’s mental health symptoms. Specifically, we discovered that children with thinner enamel tended to have higher levels of mental health symptoms, called “externalizing symptoms,” which are more outwardly observable emotional and behavior problems, such as acting out, aggression, inattention, impulsivity, hostility or distractedness. Similarly, children with smaller pulp volume also tended to have more externalizing problems. These results were true even when we accounted for other factors, such as tooth grinding, which can affect the size and shape of teeth, and socio-economic status, which we know is one of the strongest predictors of externalizing symptoms. Although these results are preliminary and must be repeated in other studies, they are exciting.
Did you come across other interesting findings during your research?
The incisors record life experiences that happened during pregnancy or in the child’s first year of life, whether it’s related to the mother’s nutrition or experience of stress, or the child’s experience of these factors. This means that our research findings suggest that pregnancy may be a sensitive period when the foundation of vulnerability to mental health problems begins and that teeth might provide a way to measure the effects of experiences during pregnancy. At this stage, however, we do not exactly know what it is that teeth are recording or what is causing the enamel to be thinner and pulp volume to be smaller.
What is the overall importance of the study, and what do you intend working on next?
What completely blew me away is the untapped potential of this research topic. I often ask myself: Have we been ignoring teeth, a biomarker that could potentially reveal all of this useful information? Imagine if all of these useful new insights were stored within a resource that most parents either keep in a drawer or throw away!
This whole area of science is really remarkable owing to the little attention that has been given to using teeth in psychiatry. Anthropologists, archaeologists or dentists constantly have to focus on teeth, but for researchers in the field of mental health, this is very new. If there is potential evidence in children’s teeth of their future risk of mental health problems, then the opportunities for prevention would be extraordinary. However, since so few studies have been done in this area and the findings from our study are based on a small number of participants, what we really need to do is follow up on this study and determine whether we see the same sorts of signatures in the teeth of other children, and whether we see them in other types of teeth.
This field is still in its infancy, and there is so much more work that needs to be done. However, we are eager to build new collaborations, and we encourage those who may be interested in working with us to reach out.
Thank you very much for the interview.