Externalizing Behavior and Stress System Functioning in Infants Exposed to Early Adversity: A Multi-system Exploration

• In Event: 2-073 - Early Adversity, Biology, and Behavior: Examining Biological Consequences and Contingencies of Early Life Stress

Integrative Statement

BACKGROUND. Children who experience early adversity often show disruptions in regulation across multiple stress response systems, including the hypothalamic pituitary adrenal (HPA) axis and sympathetic nervous system (SNS). Alterations in salivary cortisol (a marker of HPA axis functioning) and alpha-amylase (a marker of SNS functioning) may, in turn, place children at risk for externalizing behavior problems. Indeed, low morning cortisol and a blunted diurnal cortisol rhythm have been linked with increased behavior problems (Alink et al., 2008; Bernard et al., 2015). Studies examining associations between alpha-amylase and behavior problems have found support for both high and low levels of the biomarker predicting externalizing behavior (Keller & El-Sheikh, 2009). Researchers have also suggested that the interaction between cortisol and alpha-amylase may be an important predictor of externalizing problems, with evidence that high basal cortisol predicts externalizing behavior when combined with high alpha-amylase (El-Sheikh et al., 2008). The goal of this study was to explore the independent and interactive effects of diurnal cortisol and alpha-amylase on externalizing problems among a sample of infants with high levels of environmental stress.

METHODS. Participants included 179 mothers and their 6- to 20-month old infants recruited from a high-risk neighborhood. The sample was predominantly low-income (91.6%) and ethnic minorities (96.5%). Mothers reported on children’s externalizing behavior using the Infant Externalizing Questionnaire (IEQ; Lorber et al., 2014) and their current depression symptoms using the Center for Epidemiological Studies Depression Questionnaire (CES-D; Radloff, 1977). Cumulative risk was calculated as a sum of six dichotomized risk factors, as reported by mothers, including: poverty [91.6%], education less than high school [31.8%], single parenthood [58.7%], under age 21 when child was born [14.5%], currently homeless or living in public housing [61.5%], and involvement with child protective services [30.7%], M = 2.93, SD = 1.33. Parents collected saliva samples from their children twice daily (wake-up and bedtime) over three consecutive days. Diurnal cortisol and alpha-amylase were modeled using latent difference scores, with the intercept representing morning values. Four models were tested, examining the effects of (1) cortisol alone, (2) alpha-amylase alone, (3) cortisol and alpha-amylase diurnal slope interaction, and (4) cortisol and alpha-amylase intercept interaction on infant aggression, controlling for cumulative risk and maternal depression.

RESULTS. As shown in Table 1, there were no independent effects of cortisol or alpha-amylase slopes or intercepts on infant externalizing behavior. In addition, there was no interaction effect of diurnal cortisol and alpha-amylase slopes. However, there was a significant interaction effect of cortisol and alpha-amylase intercepts on infant externalizing behavior (B = 3.69, p = .024), such that heightened morning cortisol predicted increased problem behavior when morning alpha-amylase was high (B = 2.23, p = .007), but not low (B = -0.01, p = .99; See Figure 1).

DISCUSSION. Results suggest that high morning cortisol may be a risk factor for externalizing problems in the context of high morning alpha-amylase. This study highlights the importance of examining multiple systems when characterizing the physiological correlates of externalizing problems among young children experiencing adversity.

Authors

• Allison Frost, Stony Brook University
  Presenting Author

• Melanie Rodriguez, Stony Brook University
  Non-Presenting Author

• Steven Imrisek, Stony Brook University
  Non-Presenting Author

• Allison Dash, Power of Two
  Non-Presenting Author

• Kristin Bernard, Stony Brook University
  Non-Presenting Author