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Cortisol concentrations in 12- to 18-month-old infants: stability over time, location, and stressor
Susan Goldberg1, Robert Levitan, Eman Leung
1Integrative Biology, The Hospital for Sick Children, Toronto, Canada.
Insights
Infant cortisol stress response (CSR) is stable by 12-18 months, supporting its use in developmental research. However, peak cortisol levels vary, suggesting sampling beyond 30 minutes is necessary.
Area of Science:
- Developmental psychology
- Endocrinology
- Neuroscience
Background:
- Limited understanding of early hypothalamic pituitary adrenal (HPA) axis development in infants.
- Lack of data on infant stress hormone regulation and psychopathology vulnerability.
Purpose of the Study:
- To determine if infant cortisol stress response (CSR) is a reliable endocrine phenotype for developmental stress research.
- To assess the stability of CSR parameters in infants.
Main Methods:
- Saliva samples collected pre- and post-stressor (20, 40 min) in 27 infants (12-18 months).
- Two stressors administered one week apart; home samples collected for baseline stability.
- Assessed stability of CSR across time, location, and stressors.
Main Results:
- Baseline cortisol, peak percent change, and area under the curve (AUC) were stable across conditions.
- Peak cortisol response occurred at 20 min for 50% of infants and 40 min for 50%.
- Peak response timing was inconsistent across stressors for 56% of infants.
Conclusions:
- Infant CSR and baseline cortisol are stable by 12-18 months of age.
- Inconsistent peak response times necessitate sampling infant CSR beyond 30 minutes.
- Infant CSR, especially AUC, is a valid endocrine phenotype for developmental stress research.
Background:
Sparse information on early development of hypothalamic pituitary adrenal (HPA) axis responsivity in human infants limits our understanding of stress hormone regulation and vulnerability to psychopathology. We considered whether infant cortisol stress response (CSR) is a suitable endocrine phenotype for developmental stress research.
Methods:
We assessed stability of key CSR parameters across time, location, and stressor through saliva samples taken before and then 20 and 40 min following exposure to two stressors administered 1 week apart in 27 infants aged 12 to 18 months. Time-matched home samples were collected to control for circadian rhythm and to evaluate baseline stability.
Results:
Baseline cortisol concentrations, peak percent change, and area under the curve (AUC) were stable across time and stressors. Following both stressors, half the infants exhibited peak cortisol concentrations at 20 min poststress; half peaked at 40 min poststress. For 56% of the infants, peak response time was inconsistent across stressors.
Conclusions:
In humans, baseline and CSR are stable by 12 to 18 months. Variation in CSR time course across stressors indicates that infant CSR should be sampled beyond 30 min. Results support using infant CSR, particularly as measured by AUC, as a valid endocrine phenotype for developmental stress research.
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