Child Care and Cortisol Across Infancy and Toddlerhood: Poverty, Peers, and Developmental Timing

• Author: Clancy Blair,Douglas A. Granger,Daniel Berry,
• Published date: 01 February 2016
• DOI: http://doi.org/10.1111/fare.12184
• Date: 01 February 2016

D B University of Illinois at Urbana–Champaign

C B New York University∗

D A. G Arizona State University and Johns Hopkins University∗∗

T F L P K I University of North Carolina at Chapel Hill and

The Pennsylvania State University∗∗∗

Child Care and Cortisol Across Infancy and

Toddlerhood: Poverty, Peers, and Developmental

Timing

Special Issue Guest Editor’s Note: In this arti-

cle the authors examine the extent to which the

link between children’s child care experiences

and their biophysiological functioning differs for

children experiencing heightened levels of con-

textual risk outside of child care. This research

supports the conclusion that the magnitude and

even direction of the link between child care

Department of Educational Psychology, College of

Education, No. 230B, University of Illinois, Urbana–

Champaign, 1310 S. Sixth St., Champaign, IL 61820

(djberry@illinois.edu).

∗Department of Applied Psychology, New York University,

246 Greene St. Kimball Hall, 8th Floor, New York NY

10003.

∗∗Institute for Interdisciplinary Salivary Bioscience

Research, Arizona State University, 651 E. University

Drive, P.O. Box 871104, Tempe, AZ 85287–1104; and

Center for Interdisciplinary Salivary Bioscience Research,

Johns Hopkins University, 525N. Wolfe St., Baltimore MD

21205.

∗∗∗Center for Developmental Science, 100 E. Franklin St.,

CB8115, Universityof North Carolina at Chapel Hill, Chapel

Hill, NC 27599; and Department of Human Development

and Family Studies, 110 Henderson South, Pennsylvania

State University,University Park, PA 16802.

Key Words: child care, cortisol, cumulative risk, poverty.

hours and children’s cortisol level varied for

children from high- versus low-risk contexts.

In the paired article, “Family Socioeconomic

Status, Immigration, and Children’s Transitions

Into School” (this issue, pp. 73–84), Crosnoe

and Ansari identify the personal, experiential,

and social psychological factors that affect chil-

dren’s transition from early childhood settings

to K–12 education. Their research identies the

effects of high levels of risk on children’s transi-

tion and the impact of this risk on children’saca-

demic trajectory. Crosnoe and Ansari discuss

policy and practice implications of educational

inequities associated with educational stratica-

tion.

A

Evidence suggests that relations between child

care and children’s development—behaviorally

and physiologically—likely differ between chil-

dren from high- versus low-risk contexts. Using

data from the Family Life Project (N=1,155),

the authors tested (a) whether within- and

between-child differences in children’s child

care experiences (i.e., quantity, type, care-

giver responsivity, and peer exposure) were

Family Relations 65 (February 2016): 51–72 51

DOI:10.1111/fare.12184

52 Family Relations

predictive of their cortisol levels across infancy

and toddlerhood and (b) whether these rela-

tions differed for children experiencingdifferent

levels of environmental risk. They found some

evidence of such interactive effects. For children

from high-risk contexts, within-child increases

in child care hours were predictive of cortisol

decreases. The inverse was evident for chil-

dren from low-risk contexts. This relation

grew across toddlerhood. Whereas a history

of greater center-based child care was predic-

tive of heightened cortisol levels for low-risk

families, this was not the case for children

from high-risk families. Irrespective of risk,

greater peer exposure (between children) was

associated with lower cortisol levels.

The elegant coordination of our physiological

stress systems—the fast-acting branches of the

autonomic nervous system (ANS; parasympa-

thetic and sympathetic) and the comparatively

slower hypothalamic–pituitary–adrenal (HPA)

axis—supports our abilities to negotiate the

normative demands of everyday life as well as

adjust to pronounced, real-time threats (Gunnar

& Quevedo, 2007; McEwen, 2000; Sapolsky,

Romero, & Munck, 2000). Ample evidence

illustrates that the development of these sys-

tems is highly regulated by children’s early

experiences, ranging from more distal mark-

ers of adversity (e.g., poverty; Blair & Raver,

2012) to children’s proximal experiences with

meaningful adults (e.g., parental sensitivity;

Gunnar & Vazquez, 2006; Hostinar & Gunnar,

2013). Notably, young children often spend

their time across multiple ecological contexts.

Reecting this, a well-developed literature

indicates that children’s child care experiences

can have similarly pronounced effects on HPA

axis functioning (see Geoffroy, Côté, Parent, &

Séguin, 2006; Phillips, Fox, & Gunnar, 2011;

Vermeer & van IJzendoorn, 2006).

With rare exception, however, the extant

ndings with respect to child care and children’s

adrenocortical functioning have been based on

studies of middle- to upper-income families

(though see Rappolt-Schlichtmann et al., 2009).

There is good reason to suspect that the relation

between children’s child care experiences and

their subsequent development—behaviorally

and physiologically—may be quite different for

children growing up in the context of economic

adversity (Berry et al., 2014, 2016; Côté

et al., 2007; Côté, Borge, Geoffroy, Rutter,

& Tremblay, 2008; Crosby, Dowsett, Gen-

netian, & Huston, 2010; Dearing, McCartney,

& Taylor, 2009; Votruba-Drzal, Coley, &

Chase-Lansdale, 2004). In the present study

we build on this literature substantively and

methodologically by considering (a) the degree

to which such interactive effects between child

care and environmental risk are evident in

infancy and toddlerhood and (b) the extent to

which these relations are robust to model speci-

cations that explicitly disaggregate within- and

between-child relations.

T HPA A A I  E

C

The HPA axis maintains a diurnal rhythm

marked by a daily peak after waking, a sub-

sequent decline over the course of the day,

and a nadir shortly after onset of continu-

ous sleep (Edwards, Evans, Hucklebridge,

& Clow, 2001). The diurnal pattern of HPA

activity plays important roles in a variety of

metabolic, immunological, and psychological

processes that support our day-to-day function-

ing (McEwen, 2000; Miller, Chen, & Parker,

2011). In studies of children, the preferred

assessment method of HPA axis activity is the

collection of saliva and the measurement of

cortisol (Granger et al., 2012). Cortisol is the

“end-product” hormone released into the blood-

stream from the adrenal glands—the nal step

in a biological cascade initiated by the hypotha-

lamus and perpetuated by the pituitary gland. In

addition to supporting the orchestration of sev-

eral other processes (e.g., metabolic, immune,

reproductive, and autonomic processes), mod-

erate cortisol levels are thought to support

effective neural transmission and optimal learn-

ing and high-order cognition (de Kloet, Oitzl, &

Joëls, 1999; Het, Ramlow, & Wolf, 2005).

In times of acute physiological or psycholog-

ical stress, the HPA axis mounts a particularly

pronounced response, culminating in high

levels of cortisol that reach glucocorticoid

receptors throughout the body and brain. Work-

ing with the ANS, these acute HPA stress

responses coordinate the physiological (e.g.,

cardiovascular, immune, energy production/

transportation) and psychological (e.g., atten-

tion, reex) resources needed to overcome

the stressor (Sapolsky et al., 2000). Yet, given

negative feedback processes, high cortisol