Doctor of Philosophy
Woodhouse, Susan S.
Understanding the human stress response is important because individual differences in stress response have been linked with psychological outcomes (Allwood et al., 2011). Theorists have suggested that simultaneously examining the two main components (the locus-coeruleus, norepinephrine/sympathetic nervous system (LC-NE/SNS) and the hypothalamic pituitary adrenal (HPA) axis) of the stress response system would be the most appropriate approach to further our understanding (Bauer et al., 2002). Yet most research has focused on only one component of the stress response. Further, although behavioral reactivity has been conceptualized as an important component of the overall stress response, few investigations include markers of behavioral reactivity. The purpose of the present study was to 1) identify homogenous patterns of stress reactivity across both the HPA axis and the LC-NE/SNS, 2) identify homogenous patterns when including a behavioral marker, and 3) examine whether patterns of reactivity are linked with later socio-emotional outcomes. Participants included 219 infants and their mothers who participated in a larger study of maternal caregiving. When the infants were approximately 6 months old, provided saliva samples shortly after arriving in the lab and then again, following a stressor task. Saliva samples were assayed for Cortisol (HPA) and Alpha Amylase (sAA). Infants were 37.4% Black/African American, 24.2% as biracial/multi-racial, 16.4% as White/European American, 14.6% as Latino/Hispanic, 1.4% as Asian/Asian American. Fit statistics of a Latent Profile Analysis supported a three-class solution for the LE-NE/SNS and HPA only model. Most salient was the identification of two classes with reactivity in only one system. A large heterogeneous class, with reactivity in both systems, was also identified. An additional, exploratory LPA was conducted on the infants identified as having reactivity on both systems. Again, three classes emerged, two of which were again characterized by asymmetrical reactivity. The addition of a behavioral marker for stress reactivity did not result in significant changes to infant classification. No statistically significant class differences on socio-emotional outcomes emerged, although class differences in externalizing behaviors approached significance.
Lauer, Maria, "A Multi-Systemic Analysis of Infant Stress Reactivity" (2018). Theses and Dissertations. 4299.