Chronicity and timing of poverty-related exposures on child stress responsivity: A causal inference approach for examining biological embedding of experience

• In Event: Adaptation, not deficit: Contextual and environmental influences of SES on neurodevelopment and self-regulation

Abstract

Early life experiences in the context of poverty are theorized to shape children’s developing stress response systems (SRSs; Jensen, Berens, & Nelson, 2017). While many children in poverty experience safe and supportive environments, others are at heightened risk for exposure to a multitude of environmental stressors that can adaptively calibrate these SRSs toward heightened or blunted responses to acute social stress (Ellis & Del Guidice, 2011). Although theory suggests that these trajectories may be initiated early in life, few empirical studies to date have been methodologically equipped to test questions concerned with effects of developmental timing and dose of adversity exposure in these processes. The aim of current study is to leverage an under-utilized methodological approach from the causal inference literature to begin to address these questions. Specifically, we used marginal structural models (MSMs; Robins et al., 2000)—an inverse-propensity-of-treatment weighting (IPTW) approach—to test whether the dose and/or timing of three environmental exposures across infancy and childhood impact acute stress responses (autonomic and adrenocortical) in early adolescence.

We present findings from a novel home-based Trier Social Stress Test (TSST-H) among a prospective, population-based longitudinal sample of children (N = 1,292; 48% female; 45% African American) in rural low-income communities (Family Life Project; Vernon-Feagans et al., 2013). Repeated measures of salivary cortisol (sCort), alpha amylase (sAA), respiratory sinus arrhythmia (RSA), and blood pressure (BP) were taken throughout the TSST-H to index hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system (ANS) reactivity. Latent constructs representing poverty-related exposures (material deprivation, sociocognitive resources, and psychosocial threat) were derived from measures spanning seven time points across infancy to early adolescence (DeJoseph et al., in press). After identifying potentially confounding time varying and time invariant covariates collected across the seven time points (~90 including sociodemographics and past exposures), we generated individual MSM weights representing the propensity of experiencing each exposure at each time point. We then conducted separate weighted mixed effects models of sCort, sAA, RSA, and BP to examine the putative causal effects of different patterns of exposure (no adversity, chronic adversity, and doses of adversity isolated to infancy (6 and 15 mo), toddlerhood (24 and 35 mo), and late childhood (58, 90, and 154 mo)) on children’s reactivity.

Preliminary results suggest that among children experiencing consistently little to no levels of adversity, the TSST-H elicited a typical autonomic response reflected by patterns of reactivity and recovery in sAA, RSA, and BP. With some slight differences by exposure, basal cortisol levels were generally elevated, and levels steadily declined. Evidence for dosage and possible sensitive periods also emerged across various stress systems (e.g., Figure 1), with adversity exposure in infancy and toddlerhood being particularly important for differences in patterns of reactivity in early adolescence.

The combined methodological and substantive contributions of this study elucidate the temporal and cumulative processes through which the lived experiences of children in poverty become biologically embedded. Findings have implications for developmental science as well as for programs that support families experiencing economic inequalities.

Authors

• Meriah L. DeJoseph, University of Minnesota - Twin Cities
  Presenting Author

• Isabella Chask'a Stallworthy, University of Minnesota - Twin Cities
  Non-Presenting Author

• Eric Daniel Finegood, Northwestern University
  Non-Presenting Author

• Cybele Raver, New York University
  Non-Presenting Author

• Clancy Blair, New York University
  Non-Presenting Author

• Daniel Berry, University of Minnesota - Twin Cities
  Non-Presenting Author