Hypothalamic-pituitary-adrenal axis attenuation following child sexual abuse distinguishes posttraumatic stress trajectories from late adolescence to midlife.

Biological embedding describes the process of responsive developmental adaptation whereby stress "gets under the skin." Applied to the endocrine system, early chronic stress exposure may contribute to hypothalamic-pituitary-adrenal (HPA) axis attenuation, characterized by initial elevations in cortisol followed by less steep normative increases across development due to cumulative allostatic load. Simultaneously, posttraumatic stress symptoms (PTSS), including hyperarousal and hypervigilance, may potentially reinforce HPA attenuation in a feedback loop. Prospective, longitudinal assessments of HPA attenuation are rarely undertaken, obfuscating physiological underpinnings of posttraumatic stress. Using data from 164 female participants (45.6 % with confirmed child sexual abuse exposure), we approximated HPA attenuation by estimating morning cortisol intercepts and slopes from early adolescence to early adulthood. Growth mixture modeling was then used to identify distinct longitudinal patterns of PTSS from late adolescence to midlife. Four trajectories were identified: persistently high symptoms across adulthood (High Stable), increasing symptoms emerging over time (Increasing), declining symptoms following initially elevated levels (Decreasing), and consistently low symptoms (Low Stable). Cortisol intercepts and slopes were both significantly associated with PTSS trajectory membership, such that greater HPA attenuation was linked with chronic symptoms. For example, each 1-standard deviation decrease in cortisol slope (reflecting greater HPA attenuation) was associated with nearly threefold higher odds of belonging to the High Stable PTSS trajectory relative to the Low Stable trajectory (OR = 2.97, 95 % CI [1.40, 6.31], p = .005). Findings suggest etiologically distinct pathways to chronic and delayed posttraumatic stress, underscoring the importance of biologically-informed, developmentally tailored intervention strategies.