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Developmental differences in infant salivary alpha-amylase and cortisol responses to stress

Elysia Poggi Davis1, Douglas A Granger

  • 1Department of Psychiatry and Human Behavior, University of California, Irvine, USA. edavis@uci.edu

Psychoneuroendocrinology
|March 10, 2009
PubMed

Insights

Infant stress responses change with age. Salivary alpha-amylase (sAA) reactivity to stressors develops between 2 and 6 months, while cortisol reactivity decreases.

Area of Science:

  • Developmental Psychology
  • Pediatric Health
  • Autonomic Nervous System Research

Background:

  • Infants exhibit varying physiological stress responses as they mature.
  • Understanding these developmental trajectories is crucial for assessing infant well-being and stress regulation.

Purpose of the Study:

  • To investigate age-related changes in salivary alpha-amylase (sAA) and cortisol levels in infants.
  • To examine infant physiological responses to the stress of a well-baby exam and inoculation.
  • To determine when the sympathetic nervous system's response, measured by sAA, becomes apparent in infants.

Main Methods:

  • Longitudinal study of 85 mother-infant pairs at 2, 6, 12, and 24 months.
  • Saliva samples collected pre- and post-inoculation stress during well-baby visits.
  • Analysis of salivary alpha-amylase (sAA) and cortisol levels.

Main Results:

  • Older infants (24 months) showed higher sAA levels than younger infants.
  • Stress-induced sAA increases were observed at 6 and 12 months, but not at 2 or 24 months.
  • Cortisol increases in response to stress were present at 2 and 6 months, diminishing in older infants.
  • Maternal and infant sAA levels correlated at 6, 12, and 24 months, but not at 2 months.

Conclusions:

  • The sympathetic nervous system's association with sAA secretion develops between 2 and 6 months of age.
  • Infant sAA levels become responsive to painful stressors during this developmental window.
  • Cortisol stress reactivity appears to decrease with age beyond 6 months.

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