The cortisol awakening response in toddlers and young children

The cortisol awakening response (CAR) is frequently assessed in psychoneuroendocrinological research on adult participants. However, knowledge on the development of the CAR during early life is scarce and characterized by inconsistent findings. We have recently shown that a positive CAR is readily observable in young infants under conditions of strict methodological control. However, it still remains unknown whether a significant CAR is maintained consistently throughout toddler- and childhood. Here, we report data from 150 toddlers and young children aged 12–87 months in whom salivary cortisol levels were assessed 0 and 30min post-awakening over three non-consecutive study days. High quality of data was ensured by the use of objective measures to verify children's awakening times (wrist actigraphy) and sampling times (electronic monitoring containers). Results revealed the presence of a significant CAR (>1.5nmol/L) in 142 (out of 150) children and on a total of 82% of study days. A marked CAR was consistently observed throughout all examined age groups (mean increase: 8.73nmol/L). In addition, the level of cortisol on awakening was found to increase linearly with children's age (r=.17, p=.04). Overall, the current findings strongly suggest that, contrary to previous propositions, the CAR is maintained consistently throughout toddler- and childhood

Effect of a naturalistic prospective memory-related task on the cortisol awakening response in young children

Activation of prospective memory (PM) representations following awakening has been proposed to modulate expression of the cortisol awakening response (CAR). However, experimental testing of this hypothesis is still missing. This study examined the effect of a naturalistic PM-related manipulation on the CAR in a sample of 35 preschool-aged children. The CAR was assessed on two study days (0 and 30min post-awakening) using objective verification of awakening and sampling times. Children had to remember to perform a naturalistic PM-related task (reminding their parents about a gift) on the experimental day while there was no intervention on the control day (counterbalanced order). Results revealed an increased CAR on the experimental day (mean±SD increase: 9.97±7.05nmol/L) compared to the control day (mean±SD increase: 5.45±8.14nmol/L; p=.022). Our findings concur with the notion that expression of the CAR is modulated by post-awakening anticipatory processes involving activation of PM representations

The cortisol awakening response in infants: Ontogeny and associations with development-related variables

The cortisol awakening response (CAR) is a frequently used measure in psychoneuroendocrinological research, however, some of its more fundamental aspects still require attention. An important question in this respect concerns the ontogeny of the CAR. Data from two recent reports suggest that the CAR may only emerge relatively late during child development (≥16 months of age). However, as both enquiries did not use objective means of verifying participant adherence or infants’ awakening times, it is unclear whether methodological factors may have contributed to these results. Here, we report data from a study on 33 infants aged 2–12 months with close care being taken to ensure the accuracy of sampling times by using wrist actigraphy and electronic monitoring containers. Salivary cortisol levels were assessed at 0 and 30min post-awakening over three study days. Results revealed evidence for a significant CAR (≥2.5nmol/L) in 32 (out of 33) infants and on a total 86.9% of study days, with a marked magnitude of the CAR across infants (mean estimated increase=12.54nmol/L). In addition, the cortisol level on awakening and the CAR were found to be associated with different aspects of infant's physical and sleep-related development as well as with their weight and body mass index (BMI) at birth. Contrary to previous reports, the current results thus indicate that the ontogeny of the CAR occurs at an early stage of development and that it is present from as early as two months of life. The data also suggest that post-awakening cortisol secretion may undergo considerable changes during the first year of life associated with different aspects of infant development