Subjects: Psychology >> Other Disciplines of Psychology submitted time 2024-05-10
Abstract： The Cortisol Awakening Response (CAR) is closely associated with individual psychological health. Traditional studies have used the mean value of CAR over several days to explore this relationship; however, research conclusions have been highly inconsistent due to the influence of state-dependent factors such as sleep. Therefore, this study introduces CAR variability across multiple days as a novel measure to quantify CAR and investigates its relationship with psychological health by considering trait anxiety and psychological resilience as key variables under controlled or manipulated sleep efficiency scenarios. It was hypothesized that under controlled sleep efficiency conditions, smaller CAR variability reflects positive psychological health characteristics, specifically higher psychological resilience scores and lower trait anxiety scores. Conversely, under manipulated sleep efficiency conditions, greater CAR variability was hypothesized to better reflect positive psychological health characteristics, specifically higher psychological resilience scores and lower trait anxiety scores. Two experiments were conducted to test these hypotheses. In Experiment 1, 28 participants reduced CAR variability by increasing sleep efficiency stability under three similar natural sleep days. In Experiment 2, 41 participants experienced a full night of sleep deprivation following two natural sleep days to increase CAR variability. All participants wore a sleep wristwatch to assess their sleep efficiency during the experimental period and provided four saliva samples at awakening and at 30, 45, and 60 minutes post-awakening to assess CAR. The Trait Anxiety Inventory (TAI) and the Connor-Davidson Resilience Scale (CD-RISC) were used as key variables reflecting individual psychological health. Finally, the relationship between CAR variability over multiple days and trait anxiety/psychological resilience was examined. Experiment 1 found no significant differences in participants’ sleep efficiency or CAR across the three natural sleep days. Additionally, a significant positive correlation was observed between CAR variability and trait anxiety scores over the three days, indicating that smaller CAR variability in a stable environment is associated with lower levels of trait anxiety. Experiment 2 found no significant differences in participants’ sleep efficiency and CAR across the first two natural sleep days. However, on the third day, following a full night of sleep deprivation, CAR showed a marked blunting, with post-deprivation CAR levels significantly lower than those on the preceding two natural sleep days. Moreover, Experiment 2 found a significant positive correlation between CAR variability before and after sleep deprivation and psychological resilience. This suggests that higher CAR variability in a changing environment is associated with higher levels of psychological resilience. When the traditional CAR mean was used as a measure to explore its relationship with trait anxiety and psychological resilience, no significant correlations were found in either experiment. These results indicate that CAR variability is a reliable physiological indicator of psychological health. Smaller CAR variability in stable environments is associated with lower levels of trait anxiety, whereas greater CAR variability in more variable environments is associated with higher levels of psychological resilience. This study emphasizes the importance of considering CAR variability over multiple days to understand how individuals adapt to daily stressors and challenges, providing new perspectives and evidence for promoting psychological health and designing effective intervention strategies in the future.
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