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Stability and change in cortisol and behavioral response to stress during the first 18 months of life

M Lewis1, D Ramsay

  • 1Institute for the Study of Child Development, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick 08903-0019, USA.

Developmental Psychobiology
|December 1, 1995
PubMed

Insights

Infant cortisol stress responses stabilize by 6 months of age. Individual differences in adrenocortical functioning emerge by this time, influencing later stress reactivity.

Area of Science:

  • Developmental psychology
  • Neuroendocrinology
  • Pediatric health

Background:

  • Infant stress responses, including cortisol levels, are known to change during the first year of life.
  • Previous research indicates a decline in cortisol response between 2 and 6 months.
  • Individual differences in stress reactivity begin to emerge around 4 to 6 months of age.

Purpose of the Study:

  • To observe cortisol and behavioral responses to routine inoculation in infants at 18 months.
  • To examine the stability and developmental trajectory of infant stress responses from 2 to 18 months.
  • To identify the age at which consistent individual differences in adrenocortical functioning emerge.

Main Methods:

  • Longitudinal study observing infants at 2, 4, 6, and 18 months of age.
  • Measurement of cortisol levels in response to routine inoculation (perturbation).
  • Analysis of the magnitude and consistency of cortisol responses over time.

Main Results:

  • Infants exhibited increased cortisol levels at 18 months post-inoculation.
  • The magnitude of the 18-month cortisol response was comparable to the 6-month response.
  • Cortisol response at 18 months correlated with the 6-month response, but not with 2 or 4-month responses.

Conclusions:

  • A developmental shift in adrenocortical functioning occurs by 6 months of age.
  • Consistent individual differences in cortisol stress responses are established by 6 months.
  • Early infant stress reactivity patterns show stability from 6 months onwards.

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