NICHD B1Watamura

NICHD B1Watamura - Child Development July/August 2003...

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Morning-to-Afternoon Increases in Cortisol Concentrations for Infants and Toddlers at Child Care: Age Differences and Behavioral Correlates Sarah E. Watamura, Bonny Donzella, Jan Alwin, and Megan R. Gunnar This study examined salivary cortisol, a stress–sensitive hypothalamic-pituitary-adrenocortical (HPA) axis hormone in 20 infants (12 females; M age 5 10.8 months) and 35 toddlers (20 females; M age 5 29.7 months) in full-day, center-based child care. Samples were taken at approximately 10:00 a.m. and 4:00 p.m. at child care and at home. At child care, 35% of infants and 71% of toddlers showed a rise in cortisol across the day; at home, 71% of infants and 64% of toddlers showed decreases. Toddlers who played more with peers exhibited lower cortisol. Controlling age, teacher-reported social fearfulness predicted higher afternoon cortisol and larger cortisol increases across the day at child care. This phenomenon may indicate context-specific activation of the HPA axis early in life. During the first years of life, children move from having very limited social skills to operating as skilled social partners with adults and peers (John- son, Christie, & Yawkey, 1999). In the context of full- day center-based child care, children must learn to navigate a multifaceted social and cognitive envir- onment with many same-age peers who are also contributing to social complexity. In recent investi- gations, it has been found that preschool-age children (3–5 years) may respond physiologically to the challenge of navigating this complex social environment with increased cortisol production over 1999; Dettling, Parker, Lane, Sebanc, & Gunnar, 2000; Tout, de Haan, Kipp-Campbell, & Gunnar, 1998; Cortisol is the primary hormonal product of the hypothalamic-pituitary-adrenocortical (HPA) axis. As part of the body’s normal regulatory functions, cortisol production follows a circadian rhythm with the highest level around 30 min after wake-up, followed by a sharp decrease over the next hour or two, and then a more gradual decline over the remaining daytime and evening hours (Kirschbaum et al., 1990). There is some evidence to suggest that 10% to 15% of adults do not show this typical diurnal rhythm but instead show a relatively flat pattern of cortisol production across the day (Stone et al., 2001). An early morning peak and evening nadir in cortisol levels can be observed at least as early as 3 months of age (Larson, White, Cochran, Donzella, & Gunnar, 1998; 1983). However, until children are around 3 or 4 years of age and begin to give up their afternoon naps, midmorning and midafternoon levels at home levels are also sensitive to physical and emotional Stressors typically increase cortisol over basal levels
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NICHD B1Watamura - Child Development July/August 2003...

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