Abstract
Traumatic injury is linked increasingly to alterations in both stress response systems and psychological health. We investigated reactivity of salivary analytes of the hypothalamic-pituitary-adrenal axis (cortisol) and autonomic nervous system (salivary alpha amylase, sAA) during a psychosocial stress procedure in relation to psychological health outcomes. In a prospective cohort design, stress reactivity of children ages 8 to 15 years hospitalized for traumatic brain injury (TBI; n = 74) or extracranial injury (EI; n = 35) was compared with healthy controls (n = 51) 7 months after injury. Area under the curve increase (AUCinc) assessed pre-stressor to post-stressor cortisol and sAA values. Multi-variable general linear models evaluated demographic, family functioning, group, cortisol, and sAA AUCinc, and their interactions in relation to concurrent child and parent ratings of emotion regulation and internalizing and externalizing problems. Although AUCinc values were similar across groups, their relations with outcomes varied by group. Higher stress reactivity is typically associated with fewer adjustment problems. Relative to controls, greater sAA reactivity was associated with greater emotion dysregulation after TBI. In contrast, the relation of sAA reactivity with internalizing and generalized anxiety scores was flatter for both TBI and EI groups. The flattened and/or reversed direction of sAA reactivity with psychological health outcomes after TBI, and to a lesser degree EI, suggests autonomic nervous system dysregulation. Across groups, sAA reactivity interacted with sex on several psychological health outcomes with greater dysregulation in girls than in boys. Our findings highlight altered sAA, but not cortisol reactivity, as a potential mechanism of biological vulnerability associated with poorer adjustment after TBI.