Poster #23 - Simultaneous Consideration of the SNS (alpha-amylase) and HPA (cortisol) in 6-month-old Infants’ Response to Stress

• In Event: 1-061 - Poster Session 02
  In Poster Session: PS 02 Section - Biological Processes: Psychophysiology

Integrative Statement

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).

Current understandings of the structural and functional outlines of the HPA axis and the LC-NE/SNS suggest that these two systems are integrated and cross-regulatory (Boyce & Ellis, 2005). Bauer et al. (2002) proposed a model of the possible relations between the HPA axis and the LC-NE/SNS. Bauer and colleagues’ (2002) model of stress reactivity builds on an earlier model of optimal arousal by Chrousos and Gold (1992). In this model they propose that a non-linear relationship exist. They suggest that an inverted U shape may best characterize the links between overall (i.e., both HPA and SNS) arousal and well-being. This model indicates that there is an optimal level of arousal that leads to the most adaptive response, and that insufficient or extreme overall arousal impairs the organism’s ability to respond.

The present study sought to examine this proposed model by analyzing, via a person-centered approach, patterns of stress reactivity that emerged in 6-month-old infants, following exposure to a stressor task (arm restraint).

Participants included 219 infants and their mothers who participated in a larger study of maternal caregiving. Saliva samples were collected shortly after arriving in the lab and then again at 10, 20, 30 and 40 minutes 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 (see Table 1 and Figure 1). 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. Findings will be discussed in relation to existing theories of stress reactivity.

Authors

• Maria Lauer, Children's National Health System
  Presenting Author

• Susan S. Woodhouse, Lehigh University
  Non-Presenting Author