Variability in cortisol awakening response related to sleep efficiency and its relationship with trait anxiety and psychological resilience

doi:10.3724/SP.J.1041.2025.0084

Abstract

Abstract:

The relationship between the cortisol awakening response (CAR) and individual mental health remains debated. To address this, the present study introduces CAR variability across multiple days as a novel indicator, aiming to resolve inconsistencies in prior findings often caused by situational factors affecting the traditional mean CAR measure. We investigate the association between CAR variability and both trait anxiety and psychological resilience. In Experiment 1, we reduced CAR variability by minimizing sleep efficiency variation under natural sleep conditions, finding a significant positive correlation between CAR variability and trait anxiety scores. This suggests that lower CAR variability in stable conditions correlates with lower trait anxiety. In Experiment 2, CAR variability was increased through total sleep deprivation, revealing a significant positive correlation between CAR variability and psychological resilience. This indicates that greater CAR variability in dynamic conditions corresponds with higher psychological resilience. In contrast, CAR mean levels across both experiments showed no significant associations with either trait anxiety or psychological resilience. These findings suggest that, beyond mean CAR levels, CAR variability may serve as a more effective physiological indicator of mental health. Considering CAR variability across multiple days is crucial for understanding how individuals adapt to daily life stressors and challenges, providing new perspectives and potential avenues for promoting mental health and developing effective intervention strategies.

Key words: Cortisol awakening response (CAR), variability, sleep efficiency, trait anxiety, psychological resilience

YANG Zijian, ZHAO Xiaolin, GUO Kaige, LUO Jiahao, DU Tengfei, ZHANG Yajie, HU Yueqin, YANG Juan. (2025). Variability in cortisol awakening response related to sleep efficiency and its relationship with trait anxiety and psychological resilience. Acta Psychologica Sinica, 57(1), 84-99.

Figures/Tables 13

Table 1 Descriptive Statistics for Sleep Efficiency

Sleep Efficiency Type	Collection Day	Mean (%)	Standard Deviation
Objective Sleep Efficiency	Day 1	96.00	3.09
	Day 2	95.84	3.34
	Day 3	95.87	4.59
Subjective Sleep Efficiency	Day 1	88.33	6.00
	Day 2	89.41	4.89
	Day 3	89.22	5.84

Figure 1. Differences in Cortisol and Daily CAR Indicators.
Note: Mnlnc represents CAR quantified by calculating the average increase in cortisol levels in the morning. max-min represents CAR quantified by calculating the range of cortisol level fluctuations in the morning.

Table 2 Descriptive Statistics of Variables in the Mean-Based Framework

Indicator	Mean	Standard Deviation
Subjective Sleep Efficiency (%)	95.98	3.10
Objective Sleep Efficiency (%)	88.91	4.53
Mnlnc	0.33	0.52
max?min	1.10	0.40
Trait Anxiety	41.68	7.76
Psychological Resilience	87.71	11.79

Table 3 Partial Correlations Between Mean CAR and Trait Anxiety/ Psychological Resilience, Controlling for Mean Objective Sleep Efficiency and Gender

Mean CAR Indicator	Trait Anxiety	Psychological Resilience
Mnlnc	?0.22	?0.038
max?min	0.27	?0.14

Table 4 Descriptive Statistics of Variables in the Variability-Based Framework

Indicator	Mean	Standard Deviation
Subjective Sleep Efficiency (%)	1.86	1.75
Objective Sleep Efficiency (%)	3.37	2.22
Mnlnc	0.74	0.26
max?min	0.63	0.24
Trait Anxiety	41.68	7.76
Psychological Resilience	87.71	11.79

Table 5 Partial Correlations Between CAR Variability and Trait Anxiety/Psychological Resilience, Controlling for Subjective Sleep Efficiency Variability and Gender

CAR Variability Indicator	Trait Anxiety	Psychological Resilience
Mnlnc	0.48^*	?0.026
max?min	0.13	?0.053

Figure 2. Residual Scatter Plot of CAR Variability Indicator and Trait Anxiety.
Note: Mnlnc represents CAR variability calculated by taking the standard deviation of the average increase in morning cortisol levels over three days.

Figure 3. Differences in Cortisol and Daily CAR Indicators.
Note: Significance (two-tailed test): *p < 0.05; **p < 0.01; ***p < 0.001. TSD represents the Total Sleep Deprivation day. Mnlnc represents CAR calculated by the average increase in morning cortisol levels. max-min represents CAR calculated by the range of cortisol level fluctuations in the morning.

Table 6 Descriptive Statistics of Variables in the Mean-Based Framework

Indicator	Mean	Standard Deviation
Daily Stress	3.11	1.19
Mnlnc	0.41	0.56
max?min	1.22	0.48
Trait Anxiety	50.52	1.80
Psychological Resilience	56.43	13.04

Table 7 Partial Correlations Between Mean CAR and Trait Anxiety/Psychological Resilience, Controlling for Mean Daily Stress and Gender

Mean CAR Indicator	Trait Anxiety	Psychological Resilience
Mnlnc	?0.077	0.16
max?min	0.11	?0.15

Table 8 Descriptive Statistics of Variables in the Variability-Based Framework

Indicator	Mean	Standard Deviation
Daily Stress Variability	0.44	0.36
Mnlnc	0.78	0.27
max?min	0.69	0.24
Trait Anxiety	50.52	1.80
Psychological Resilience	56.43	13.04

Table 9 Partial Correlations Between CAR Variability and Trait Anxiety/Psychological Resilience, Controlling for Daily Stress Variability and Gender

CAR Variability Indicator	Trait Anxiety	Psychological Resilience
Mnlnc	?0.022	?0.085
max?min	0.12	0.36^*

Figure 4. Residual Scatter Plot of CAR Variability Indicator and Psychological Resilience.
Note: max-min represents CAR variability calculated by taking the standard deviation of the range of morning cortisol level fluctuations over three days.

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