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Developmental changes in baseline cortisol activity in early childhood: Relations with napping and effortful control
Author(s) -
Watamura Sarah E.,
Donzella Bonny,
Kertes Darlene A.,
Gunnar Megan R.
Publication year - 2004
Publication title -
developmental psychobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 93
eISSN - 1098-2302
pISSN - 0012-1630
DOI - 10.1002/dev.20026
Subject(s) - bedtime , medicine , hydrocortisone , endocrinology , cortisol awakening response , el niño , circadian rhythm , multilevel model , computer science , machine learning
Development of the hypothalamic–pituitary–adrenocortical (HPA) axis was examined using salivary cortisol levels assessed at wake‐up, midmorning, midafternoon, and bedtime in 77 children aged 12, 18, 24, 30, and 36 months, in a cross‐sectional design. Hierarchical linear modeling (HLM) analyses were used to characterize cortisol production across the day and to examine age‐related differences. Using area(s) under the curve (AUC), cortisol levels were higher among the 12‐, 18‐, and 24‐month children than among the 30‐ and 36‐month children. For all five age groups, cortisol levels were highest at wake‐up and lowest at bedtime. Significant decreases were noted between wake‐up and midmorning, and between midafternoon and bedtime. Unlike adults, midafternoon cortisol levels were not significantly lower than midmorning levels. Over this age period, children napped less and scored increasingly higher on parent reports of effortful control. Among the 30‐ and 36‐month children, shorter naps were associated with more adultlike decreases in cortisol levels from midmorning to midafternoon. Considering all of the age groups together, effortful control correlated negatively with cortisol levels after controlling for age. These results suggest that circadian regulation of the HPA axis continues to mature into the third year in humans, and that its maturation corresponds to aspects of behavioral development. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 45: 125‐133, 2004.