Cortisol Awakening Response
The cortisol awakening response (CAR) is an increase between 38% and 75% in cortisol levels peaking 30–45 minutes ''after'' awakening in the morning in some people. This rise is superimposed upon the late-night rise in cortisol which occurs ''before'' awakening. While its purpose is uncertain, it may be linked to the hippocampus' preparation of the hypothalamic-pituitary-adrenal axis (HPA) in order to face anticipated stress. Description Shortly after awakening, a sharp 38–75% (average 50%) increase occurs in the blood level of cortisol in about 77% of healthy people of all ages. The average level of salivary cortisol upon waking is roughly 15 nmol/L; 30 minutes later it may be 23 nmol/L, though there are wide variations. The cortisol awakening response reaches a maximum approximately 30 minutes after awakening though it may still be heightened by 34% an hour after waking. The pattern of this response to waking is relatively stable for any individual. T ...
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