The cortisol awakening response: Fact or fiction?
Clara Velazquez Sanchez1, Jeffrey W Dalley1,2
1Department of Psychology, University of Cambridge, Cambridge, UK.
Brain and Neuroscience Advances
|April 29, 2025
Summary
The cortisol awakening response may not be triggered by waking itself, but rather a continuation of circadian rhythms. This study found cortisol secretion rates didn't change upon waking, highlighting the complexity of this response.
Area of Science:
- Endocrinology
- Chronobiology
- Neuroscience
Background:
- The cortisol awakening response (CAR) is a well-documented phenomenon.
- Its origins, whether driven by the act of waking or an underlying circadian rhythm, remain debated.
- Disturbances in CAR are linked to stress-related disorders.
Purpose of the Study:
- To investigate the origin of the cortisol awakening response.
- To determine if cortisol release increases due to the waking process or circadian rhythm continuation.
- To analyze factors influencing CAR variability.
Main Methods:
- Employed an innovative in vivo microdialysis technique.
- Measured tissue-free cortisol levels in 201 healthy volunteers.
- Collected data in a home setting before and after awakening.
Main Results:
- The rate of cortisol secretion did not significantly change upon waking compared to sleep.
- Considerable between-subject variability in cortisol release was observed.
- Sleep duration and waking timing partially explained this variability.
Conclusions:
- The findings challenge the notion that waking directly triggers the cortisol awakening response.
- Cortisol release patterns around waking are complex and influenced by individual factors.
- Caution is advised when interpreting post-awakening cortisol measurements solely.
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