Children’s Diurnal Cortisol: Heritability and Relations with Peer Relationships

• In Event: Poster Session 02
  In Poster Session: PS 02 Topic - Biological Processes: Neuroscience and Genetics

Abstract

Cortisol is the primary end product of the hypothalamic-pituitary-adrenal (HPA) axis, that helps one to adapt to meet environmental demands. The underlying components of HPA functioning may be partly heritable, but differentially related to the context (Shirtcliff & Essex, 2008). Twin studies have reported higher heritability for morning cortisol, with afternoon cortisol largely determined by the environment (Van Hulle et al., 2012). In addition, afternoon values for mothers, fathers, and twin children were correlated due to their shared environment rather than shared genetics (Schreiber et al., 2006). We aimed to replicate heritability findings, and extend the literature by considering peer relationships. By middle childhood, children spend approximately 30% of their social interactions with peers (Rubin et al, 2006). Specifically, given the importance of the context for afternoon cortisol values, we hypothesized that afternoon cortisol would be related to peer relationships.
Families are part of a longitudinal twin study (N = 688 children, 51.8% female, Mage = 8.44 years, >31% Latinx; 45.8% below middle class; Lemery-Chalfant et al., 2013). To measure diurnal cortisol, saliva samples were collected three times/day over three consecutive typical weekdays: at wake-up, afternoon, and bedtime. Measures of diurnal cortisol include AM slope, PM slope, and AUC (area under the curve), averaged across days. Primary caregivers also completed Positive Peer Relationship scales from the MacArthur Health and Behavior Questionnaire. We fit ACE models estimating genetic and environmental influences with the effects of age, sex, batch, and vacation collection regressed out of raw variables (McGue & Bouchard, 1984).
Intercorrelations, twin intraclass correlations, and descriptive statistics are provided in Table 1. Cortisol AUC was moderately and negatively correlated with AM and PM Slopes, whereas AM and PM Slopes were not correlated. In addition, cortisol AUC was modestly and negatively correlated with Positive Peer Relationships, but AM and PM cortisol slopes were not related. Standardized estimates of ACE factors for AUC, AM Slope, PM Slope, and Positive Peer Relationships, and fit statistics of full and best fitting reduced models are given in Table 2. For Cortisol AUC, the full model best represented the data, with modest additive genetic and nonshared environmental influence (.35 and .21, respectively) and moderate shared environmental influence (.44). For AM Slope, the best fitting reduced model was an AE model, with high additive genetic influence (.66) and modest nonshared environmental influence (.34). For PM Slope, the best fitting reduced model was a CE model, with modest shared environmental influence (.12) and high nonshared environmental influence (.88). Finally, for Positive Peer Relationships, the full model best represented the data, with moderate additive genetic and shared environmental influences (.40 and .43, respectively) and modest nonshared environmental influence (.17).
Overall, findings support and extend previous twin studies that show heritability of children’s diurnal cortisol is highest in the mornings, with afternoon values largely determined by the environment. Although cortisol AUC was negatively related to peer relationships, we did not extend previous findings that afternoon, compared to morning values, more closely map to social relationships.

Authors

• Kathryn Lemery-Chalfant, Arizona State University
  Presenting Author

• Karina R. Sokol, Glendale Community College
  Non-Presenting Author

• Veronica Oro, University of Oregon
  Non-Presenting Author

• Emma Lecarie, Arizona State University
  Non-Presenting Author

• Gianna Rea-Sandin, University of Minnesota - Twin Cities
  Non-Presenting Author

• Leah D Doane, Arizona State University
  Non-Presenting Author