According to the “prenatal programming of mental illness” hypothesis, the prenatal period is one of the earliest sensitive periods in development when maternal psychosocial stress exposure can have enduring effects on offspring mental health. Currently, many measurement tools exist to characterize the occurrence of maternal psychosocial stress exposure (e.g., depression; anxiety, stressful life events, etc). However, these measures may not fully record the presence and timing of these experiences, especially when administered to mothers retrospectively. To better assess the biological consequences of maternal psychosocial stressors on children, objective tools are additionally needed to capture the prenatal and perinatal presence and timing of maternal stressful life experiences. With a broader array of available tools, our field will be better poised to identify children who are most vulnerable and intervene. Our group has been exploring children’s shed primary teeth as objective and non-invasive tools that record the occurrence and timing of pre- and perinatal stressful life events. Since teeth provide a fossilized record of their formation process, our working hypothesis is that early life stressors– and particularly the timing of these psychosocial events – can be non-invasively measured in shed teeth that began forming in utero. In this R21, we will test this hypothesis across two aims by analyzing data collected from a separately-funded study called STRONG (Stories Teeth Record of Newborn Growth). STRONG was funded in 2019 to build a biorepository of teeth from children whose mothers were exposed to the 2013 Boston Marathon Bombing and manhunt events. In Aim 1, we will use techniques standardly deployed in anthropology/archaeology (e.g., microCT imaging; histology; light microscopy) alongside newer approaches (e.g., laser confocal microscopy) to derive a stress and other markers in teeth and determine the parameters for when and how the Marathon bombing is visible in shed teeth. In Aim 2, we will pair these tooth- based measures with subjective (self-report and electronic-health records) data of the bombing exposure to compare the strength of the association between these two sets of measures on levels of child psychopathology symptoms. As far as we know, this study would be the first to determine the degree to which primary teeth mark the presence and timing of maternal psychological stress in relation to a traumatic event. If validated as biomarkers, teeth would transform the study of sensitive periods by providing a new, non-invasive measure for capturing and dating pre- and perinatal psychosocial exposures. Teeth could be used alongside existing tools to screen children for early life stress exposure and to understand its biological consequences.