Abstract
The cortisol awakening response (CAR) is a distinct facet of the circadian cortisol rhythm associated with various health conditions and risk factors. It has repeatedly been suggested that the CAR could be a result of the anticipated demands of the upcoming day (stress anticipation) and could support coping with daily life stress. In a sample of 23 healthy participants CARs were assessed on two consecutive days by measures of salivary cortisol upon awakening (S1) and 30 and 45 minutes later, which were aggregated to the area under the curve increase (AUCI). Stress anticipation was assessed immediately after awakening. On the same days, daily life stress and distress were assessed six times per day based on a quasi-randomized design using handheld computers. Associations were tested by day using regression analysis and standard multilevel/mixed effects models for longitudinal data. The CAR AUCI moderated the effect of daily life stress on distress; higher CAR increases were associated with attenuated distress responses to daily life stress on both days (day 1: p = .039; day 2: p = .004) adjusted for age, gender, sleep quality, time of awakening and oral contraceptive use. Lagged-effects and redundancy models showed that this effect was not due to prior-day CAR increases but specific for same day CARs. On day 2, associations between daily life stress and distress were stronger when individuals showed a higher S1 cortisol level, but this effect was similar for S1 on day 1, and the day 2 effect of S1 became non-significant when S1 on day 1 was controlled. No associations were found between stress anticipation and CARs. Findings indicate that the CAR increase is associated with successful coping with same-day daily life stress.
Highlights
The cortisol awakening response (CAR) is a distinct facet of the circadian cortisol rhythm, an increase of cortisol within the first hour after awakening that is separate from the cortisol increase during the second half of the night [1]
A summary of these considerations yields the following CAR anticipation hypotheses: The CAR is a distinct facet of the circadian rhythm of cortisol secretion that occurs after awakening, is linked to reactivation of information from memory based on neuronal activation processes throughout the awakening period, and serves the function of preparing the organism to deal with demands of the upcoming day
The observation of an increased CAR on competition days compared to non-competition days in competitive ballroom dancers [23] is consistent with the proposed function of preparing the organism to cope with demands of the upcoming day, it remains unclear if the increased CAR led to better performance and/or activated more performancerelevant resources
Summary
The cortisol awakening response (CAR) is a distinct facet of the circadian cortisol rhythm, an increase of cortisol within the first hour after awakening that is separate from the cortisol increase during the second half of the night [1]. Increased CARs were observed in relapsing-remitting multiple sclerosis [5], upper respiratory symptoms [6], visceral obesity [7], and women with the metabolic syndrome [8]. Decreased CARs were observed in patients with type 2 diabetes mellitus [9], chronic fatigue syndrome [10,11], systemic hypertension [12], and functional gastrointestinal disorders [13]. Clarifying underlying factors and potential consequences of the CAR might help to better understand its often ambiguous links with a variety of health conditions. Two recent longitudinal studies found that a greater CAR is a risk factor for peritraumatic dissociation and acute stress disorder [14], and for major depression [15]
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