Developmental changes in baseline cortisol activity in early childhood: relations with napping and effortful control

Area of Science:

• Developmental psychology
• Endocrinology
• Neuroscience

Background:

• The hypothalamic-pituitary-adrenocortical (HPA) axis regulates the stress response.
• Understanding HPA axis development in early childhood is crucial for identifying potential developmental trajectories.

Purpose of the Study:

• To examine the developmental trajectory of the HPA axis in children from 12 to 36 months of age.
• To investigate the relationship between HPA axis maturation, napping behavior, and effortful control.

Main Methods:

• Salivary cortisol levels were measured in 77 children at four time points daily (wake-up, midmorning, midafternoon, bedtime).
• Hierarchical linear modeling (HLM) was used to analyze age-related differences and diurnal cortisol patterns.
• Area under the curve (AUC) was calculated to assess overall cortisol exposure.

Main Results:

• Cortisol levels, assessed by AUC, were higher in younger children (12-24 months) compared to older children (30-36 months).
• Cortisol levels followed a diurnal pattern, highest at wake-up and lowest at bedtime, with significant decreases observed.
• Shorter nap durations in older children correlated with more adult-like cortisol decreases, and higher effortful control negatively correlated with cortisol levels.

Conclusions:

• Circadian regulation of the HPA axis continues to mature through the second year of life in humans.
• HPA axis maturation in early childhood is associated with behavioral development, specifically reduced napping and increased effortful control.