Teeth as Potential New Tools to Measure Early-Life Adversity and Subsequent Mental Health Risk: An Interdisciplinary Review and Conceptual Model

Abstract

Early-life adversity affects nearly half of all youths in the United States and is a known risk factor for psychiatric disorders across the life course. One strategy to prevent mental illness may be to target interventions toward children who are exposed to adversity, particularly during sensitive periods when these adversities may have even more enduring effects. However, a major obstacle impeding progress in this area is the lack of tools to reliably and validly measure the existence and timing of early-life adversity. In this review, we summarize empirical work across dentistry, anthropology, and archaeology on human tooth development and discuss how teeth preserve a time-resolved record of our life experiences. Specifically, we articulate how teeth have been examined in these fields as biological fossils in which the history of an individual's early-life experiences is permanently imprinted; this area of research is related to, but distinct from, studies of oral health. We then integrate these insights with knowledge about the role of psychosocial adversity in shaping psychopathology risk to present a working conceptual model, which proposes that teeth may be an understudied yet suggestive new tool to identify individuals at risk for mental health problems following early-life psychosocial stress exposure. We end by presenting a research agenda and discussion of future directions for rigorously testing this possibility and with a call to action for interdisciplinary research to meet the urgent need for new biomarkers of adversity and psychiatric outcomes.

Keywords: Adversity; Biomarkers; Mental health; Prevention; Stress; Teeth.

Figure 1.

The properties of teeth as records of early-life experience (images created with BioRender). Human teeth possess at least five properties that position them to be promising biomarkers of early-life adversity and subsequent depression risk. (A) Each tooth is made of enamel (the hard outermost layer of the tooth crown), dentin (the underlying layer extending into the tooth root), and pulp (the innermost core of the tooth containing blood vessels, nerve cells, and dentin-forming cells called odontoblasts). (B) Teeth develop incrementally. In the final stage of development, enamel-producing cells known as ameloblasts secrete proteins that mineralize the dentin and enamel. Enamel is laid down in a matrix of crystal rods. (C) Because enamel does not regenerate, it leaves a permanent record of its formation process in the tooth, much like the rings in a tree marking its age. Stress exposure during development can disrupt this process, producing stress lines or permanent records of the existence and timing of the stressful experience. (D) Each tooth develops over a known time scale (see hollow bars). Collection of teeth could occur at multiple times across the first two decades of life when teeth are spontaneously shed or routinely removed (see dashed bars). Each time teeth are shed or removed possibly represents an easy and inexpensive opportunity for assessment and intervention to guide primary prevention efforts for psychiatric diseases. Here, we highlight prevention for major depressive disorder as an illustrative example. These prevention efforts are made possible because the time periods for tooth availability coincide with time periods during or before major depressive disorder often first onsets (see filled bars). Photos in panel A (right) and panel B (right) are from F.B. Bidlack (unpublished data). Photo in panel C (right) is from Nanci (43).

Figure 2.

The TEETH (Teeth Encoding Experiences and Transforming Health) conceptual model (images created with BioRender). The three main tenets of the TEETH conceptual model are presented. The first states that exposure to psychosocial stressors (e.g., growing up in poverty, witnessing or experiencing violence) during early life disrupts multiple developmental processes, including those involved in brain development and programming of the body’s stressresponse circuitry and epigenome. We propose that psychosocial stressors may also affect tooth formation. The second tenet of the model states that these disruptions in development leave behind biological imprints--or markers--that can be objectively captured. Importantly, some of these markers, such as stress lines in teeth, may also preserve information about the timing of early exposures and consequent developmental disruptions. Finally, the third tenet of the model proposes that these markers of disrupted processes can be used to predict important mental health outcomes.