Do infants show a cortisol awakening response?

Abstract

Upon awakening from sleep, combined processes of deactivation of the hippocampus and activation of suprachiasmatic nucleus result in a marked increase in cortisol release from structures within the hypothalamic-pituitary-adrenal axis. This phenomenon, termed the cortisol awakening response (CAR), has been studied extensively in adults. In the current study, we examine this phenomenon for the first time in infancy. Saliva samples were collected by 32 mothers from themselves and their infants (13 males; 7.8-17.4 months of age) at the infant's AM waking (and 30 min later), and upon waking from the infant's first nap (and 30 min later). In contrast to what has been observed with the CAR in adults, cortisol levels declined from AM waking to 30 min post-waking. Moreover, cortisol levels did not significantly rise or fall following naps. Consistent with prior research, both group-level and dyadic-level analyses showed that cortisol levels for mother-infant dyads were associated.

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

“…Moreover, the magnitude (mean increase: 12.5 nmol/L) and response rate (86.9%) of the CAR which was seen in the present infant data, closely parallels or even exceeds previous data from adult participants (mean increase: 9.3 nmol/ L, see Clow et al, 2004;response rate: 85.3%, Dockray et al, 2008). Overall, the present findings thus stand at variance with previous reports showing no evidence of a positive CAR in children below the ages of 16 (Saridjan et al, 2010) 17 months (Bright et al, 2011). To compare these data with the current results, it is crucial to note that both previous studies had not objectively verified infants' times of awakening or parents' adherence to the sampling protocol.…”

“…While the CAR does not provide a marker of acute stress responsivity in adult participants (e.g., Schmidt-Reinwald et al, 1999;Prüssner et al, 2007), our findings are in line with the notion that the development of a general hyporesponsivity of the HPA axis during later infancy (see Gunnar and Donzella, 2002) may also result in an attenuation of the CAR during this period. Combining the current findings of an age-related decline in CAR magnitude over the first year of life with previous data failing to show consistent evidence of a CAR in slightly older infants (Saridjan et al, 2010;Bright et al, 2011), may even suggest the development of a relative 'quiescence period' of the CAR in infants older than 12 months of age. However, first data from an ongoing study by our research group strongly suggest that when using the same rigorous methodological approach described here, a significant CAR is also consistently observable in two to six year-old children (n = 48, unpublished observation).…”

“…A study on 366 infants aged 12-20 months revealed that on average infants below 16 months of age did not show a positive CAR (Saridjan et al, 2010). In line with this, a recently published study on 32 infants aged 7-17 months also failed to provide evidence for a positive CAR in this age group and, indeed, reported a declining pattern of cortisol levels from awakening to 30 min post-awakening (Bright et al, 2011). In a longitudinal study on somewhat older children, a positive CAR was only found in 68% of 60-month-old children and this increased to 93% at a second assessment eight months later (DeCaro and Worthman, 2008).…”

The cortisol awakening response (CAR) in toddlers: Nap-dependent effects on the diurnal secretory pattern

“…This fundamental finding suggests that cortisol is not only regulated by the circadian system (Czeisler and Klerman, 1999) but also is nap-dependent. It is important to note that our results are not consistent with earlier research indicating the absence of a CAR following a nap in older infants (Bright et al, 2012); however, that study did not use objective assessment of sleep or nap wake time, which may have resulted in parents not accurately recognizing their child’s waking state and thus missing the opportunity to capture the CAR. Whether the CAR is already present in infancy or develops sometime before the toddler years is an important empirical question that will necessitate further study using objective measures of wake time.…”

Maternal emotional availability at bedtime and infant cortisol at 1 and 3months

“…We believe that assessment of the environment in which infants are sleeping in relation to their cortisol will be an important avenue for future work. Additionally, because there is some evidence that mothers with higher cortisol reactivity display lower quality parenting (42-43), and mother and infant cortisol are positively correlated (44-47), it may be that the relations between maternal EA and infant cortisol detected in this study can by accounted for by the correlation between mother and infant cortisol. Teasing apart these associations is another area for further study.…”