What Happens to Your Stress Hormones When You Wake Up Each Morning?
Cortisol rises in the first half hour after you wake, a pattern called the cortisol awakening response (CAR). This study asked whether being a morning person or a night owl changes that pattern, and it did so under controlled conditions: 103 young men each slept one night in a sleep laboratory, were woken at 6:30 am, and gave saliva samples at 0, 15, and 30 minutes after waking, all collected under supervision. Twelve of them qualified as evening types (MEQ below 41) and 20 as morning types (MEQ above 59). Greater morningness was linked to a higher cortisol level at the moment of waking and to greater total cortisol output across the post-awakening period, but it was not linked to the size of the rise itself.
Dr. Kumar’s Take
Chronotype research has a long-standing measurement problem. Much of it relies on people collecting their own saliva at home, at the exact minute they wake, on the honor system. Earlier work had already reported a chronotype effect on the CAR, but it was collected without objective control over whether participants actually sampled when they claimed to. That is not a small caveat, because being late with the first sample changes the number you get. The design here answers that directly: the researchers put everyone in a laboratory, woke them at the same clock time, and supervised every sample. The chronotype effect survived that scrutiny, and it landed in a specific place, on the level of cortisol at awakening and on total output, not on the dynamic rise. That distinction matters clinically. A morning type and an evening type can produce the same awakening surge while sitting at different absolute cortisol levels. If you only report the rise, you miss the difference entirely. I hold the finding loosely, though, because it rests on one night per person.
Key Findings
Chronotype effects emerged consistently, both from dimensional analyses across the whole sample and from the direct comparison of morning types against evening types. Greater morningness was associated with an increased cortisol level upon awakening, the first sample taken at zero minutes.
Greater morningness was also associated with greater overall cortisol output across the sampling period, expressed as the area under the curve with respect to ground.
Morningness was not associated with the CAR itself, the area under the curve with respect to increase, which captures the rise from the waking value rather than the absolute level. Chronotype was therefore related to altered cortisol secretion over the post-awakening period without being related to the magnitude of the awakening rise.
Brief Summary
This research measured cortisol through saliva samples collected immediately upon awakening and at 15 and 30 minutes afterward. Every sample was collected under strict supervision in a sleep laboratory, which is the point of the study: recent guidelines treat objective control of participant compliance as critical for valid CAR data, and the earlier evidence on chronotype and cortisol lacked it. The sample was 103 young males, all woken at 6:30 am after a single night in the laboratory, and chronotype was classified using MEQ scores.
Study Design
All participants slept one night in a sleep laboratory and were woken at 6:30 am the following morning. Saliva samples for assessment of the CAR were collected under strict supervision at 0, 15, and 30 minutes post-awakening. Chronotype was defined by the MEQ, with scores below 41 classifying an evening type and scores above 59 classifying a morning type. Of the 103 young men, 12 met the evening type threshold and 20 met the morning type threshold. Analyses were run two ways, dimensionally across the entire sample and categorically between morning and evening types, and both produced significant chronotype effects.
Results You Can Use
The direction of the finding is consistent: the more of a morning person you are, the higher your cortisol at the moment of waking and the greater your total cortisol output over the following half hour. The rise itself, the part most people mean when they say “cortisol awakening response,” did not track with chronotype.
That split is the practical takeaway. Two people with identical awakening surges can sit at different absolute cortisol levels depending on where they fall on the morningness scale, and a measurement approach that reports only the increase from baseline will show them as identical.
The laboratory setting is what gives these numbers weight. Everyone woke at the same time, under supervision, with samples taken on schedule, which removes the compliance uncertainty that clouded the earlier literature on this question.
Why This Matters For Health And Performance
Cortisol measured in the first 30 minutes after waking is widely used as a marker in research and in clinical interpretation. If chronotype shifts the absolute level at awakening and the total output, then comparing one person’s morning cortisol to another’s without accounting for chronotype introduces a systematic difference that has nothing to do with health status.
It also sharpens what “the CAR” means. The awakening rise and the absolute post-awakening levels are separate quantities, and they respond to chronotype differently. Anyone drawing conclusions from a morning cortisol result should know which of the two was actually measured.
How to Apply These Findings in Daily Life
- Know where you fall on the MEQ: scores above 59 define a morning type and scores below 41 define an evening type in this work
- Ask which quantity was measured: the level at awakening and the total output tracked with chronotype, the rise from waking did not
- Fix the wake time before comparing mornings: every participant here was woken at 6:30 am, which is what makes the comparison clean
- Insist on verified sample timing: supervised collection is what separates this study from the earlier evidence on the same question
- Interpret a single morning as a single morning: each participant contributed one night, and I would not draw a personal conclusion from one measurement day
- Do not read a higher waking cortisol as better or worse: this is a chronotype difference, and I treat it as a difference rather than a verdict
Limitations To Keep In Mind
The authors state the main one plainly: the results have to be replicated because this is a single day study design. The sample was 103 young males, with only 12 evening types and 20 morning types meeting the categorical thresholds, so the group comparisons rested on small subsets of an otherwise narrow population. The findings describe cortisol secretion over the post-awakening period in that setting and under that fixed wake time.
Related Studies And Internal Links
How Melatonin Timing Changes with Age: DLMO Patterns Across the Lifespan
Episode 31: Depression Explained, The Biology Behind the Darkness
Episode 32: Depression Recovery Roadmap: A Step-by-Step, Evidence-Based Plan
DLMO: The Gold Standard Test for Measuring Your Circadian Clock Timing
Your Brain’s Master Clock: Suprachiasmatic Nucleus Controls Circadian Rhythms
One Week Sleep Restriction Reduces Testosterone by 15% in Young Men
FAQs
Does being a morning person change your cortisol when you wake up?
In this study, yes. Greater morningness was associated with a higher cortisol level in the sample taken immediately upon awakening, and with greater overall cortisol output across the 30 minutes that followed.
Does chronotype change the size of the cortisol awakening response itself?
No. Morningness was not associated with the CAR expressed as the increase from the waking value, even though it was associated with the absolute level and the total output.
Why did this study use a sleep laboratory instead of home sampling?
Because earlier data on chronotype and cortisol were collected without objective control of participant compliance, which current guidelines treat as critical for valid CAR data. Here, participants slept in the laboratory, were woken at 6:30 am, and gave all three samples under strict supervision.
Conclusion
Under supervised sleep laboratory conditions, chronotype was related to cortisol secretion over the post-awakening period in 103 young men. Greater morningness meant higher cortisol at the moment of waking and greater total output over the next 30 minutes, with no relationship to the size of the awakening rise. The design was a single night per participant, so the authors call for replication, and I read the result the same way: a consistent signal that still needs a second look.
