Cortisol is one multi-functioning hormone, and has been studied from every angle in adults. From stress, immune function, to fetal development; cortisol plays critical roles in our bodies. Cortisol gets a lot of press for its effect on adult metabolism, but little has been known about cortisol’s functions in babies and toddlers. Until now, that is, as the first ever study found an interesting link between cortisol and infant sleep patterns.
One area for study of cortisol has been a phenomenon known as Cortisol Awakening Response (CAR), in which blood levels of cortisol increase roughly 50% within 20-30 minutes after wakening and is thought to occur in preparation to face anticipated stress. While exactly what the purpose of CAR is remains unknown, everyone’s cortisol levels increase during sleep but decrease throughout the day; although for some people CAR levels can increase during stress, worry, anxiety, or being worn-out.
Researchers from the University of Georgia Franklin College of Arts and Sciences found that this response is exactly the opposite in infants. This is the first study to examine CAR in infants, and found it may have implications on how babies handle stress as well as how proper care from mothers could affect how growing children respond to cortisol as they grow up.
In adults, cortisol is released in response to stress (among other functions) and with respect to CAR, upon waking a team of organs known as the hypothalamic-pituitary-adrenal (HPA) axis work together to release cortisol; sort of standing on look-out to alert the body of stress or threats. However, the study found that in infants, cortisol levels stayed the same for an hour and a half after the babies woke up in the morning, and it didn’t change after naps either. The research team also discovered a mother-baby cortisol association called “psychological attunement”, confirming previous research that a mother and child’s cortisol levels are correlated.
Thirty two mom and baby pairs enrolled in the study, and moms were instructed to collect saliva samples from themselves and their babies at specific times of the day, especially after baby awoke in the morning and after the first nap of the day. Nobody knows when CAR begins in babies, or why infants do not have a rise in cortisol upon waking, but further understanding could offer clues as to how one responds to cortisol later in life. Previous research has found that women who were treated poorly as infants or children have higher cortisol levels upon waking as adults. Authors also note the psychological attunement also has implications for the mother-baby relationship, but that much more research is needed.
