Project Summary Pediatric chronic pain is a common but understudied health problem, with prevalence increasing from childhood to adolescence, particularly among girls. Moreover, prevalence rates have increased over the past 20 years for unknown reasons. Despite the high prevalence and enduring impact, we know little about its etiology and developmental progression. The literature documents associations between exposure to early adversity and chronic pain among adults, but little is known about the early developmental time course, key mechanisms, and social resilience that can mitigate risk in youth. Critical questions need to be addressed before efforts at prevention and intervention can have maximum impact. To that end, the proposed competing continuation project focuses on four aims: identify the genetic and environmental influences on growth in pain across childhood and adolescence (Aim1); examine the role of stress exposure in the development of children's chronic pain (Aim 2); and evaluate two potential mechanisms linking stress and pain, problems with emotion regulation (Aim 3), and epigenetics (Aim 4). Under a recalibration model, we also explore social resilience in adolescence as a buffer of these risk processes. To accomplish our aims, we propose to conduct intensive longitudinal follow-up assessments (at 14, 15, and 16 years of age) of a birth-records-based community sample of 350 pairs of twins who are diverse in ethnicity and socioeconomic status. Stress, emotion regulation, and recurring pain during early and middle childhood have already been well characterized. Assessments during adolescence will take a multi-method approach that includes clinical and diary assessments of pain frequency, intensity, duration; objective, diary, and questionnaire assessments of emotion regulation, stress, and social resilience; and objective assessments of epigenetics. Our genetically informed developmental approach to understanding the etiology and mechanisms of pain i