Larger Average Cortisol Awakening Response Is Associated with Poorer Executive Function and Processing Speed in Healthy Adolescents

Abstract

Background: The cortisol awakening response (CAR) refers to the sharp increase in cortisol secretion following awakening. Cortisol and the CAR have been implicated in several cognitive domains, including executive function, but past results are inconsistent. One explanation is that the CAR is influenced by environmental and psychological factors including sleep and anticipatory stress, which are rarely controlled in studies. Methods: We measured the CAR and cognitive performance in 12 healthy adolescents over 3 days. Participants stayed in a sleep laboratory with strictly controlled environment, sleep, and daily activities. Participants completed a CANTAB cognitive test battery daily, including measures of executive function, processing speed, spatial working memory, learning, and reaction time. The CAR was assessed with saliva samples at 0, 15, 30, and 45 minutes post-awakening, and quantified as the areas under the curve with respect to ground (AUCg) and increase (AUCi). Findings: We found that larger average CARs were associated with poorer executive function (attentional set-shifting) and processing speed (planning/response speed). The CAR was not associated with other cognitive measures. Interpretation: Larger trait CARs may reflect sustained, elevated cortisol, possibly contributing to gradual damage to white matter (affecting processing speed) and brain regions with high glucocorticoid expression (including those subserving executive functions). Alternatively, larger CARs and poorer cognitive performance may be common consequences of an unidentified developmental factor. Funding Statement: The Rob Pierce Grant in Aid from the Australasian Sleep Association, intramural funds (University of Adelaide). Declaration of Interests: The authors have nothing to declare. Ethics Approval Statement: Ethical approval was granted by the University of South Australia Human Research Ethics Committee, and all procedures were performed in accordance with the Declaration of Helsinki.