Does coffee raise cortisol? The 90-minute rule, checked
The advice to wait 90 minutes before your first coffee has spread fast. The study most often linked to caffeine and cortisol tells a more specific story, and it is mostly about the afternoon cup.
contentsThe short answer
Key points
- Yes. Caffeine raised cortisol across the day in people who had gone 5 days without it.
- In daily drinkers, the first morning dose no longer raised cortisol. Later doses still did.
- No study we found tested waiting 90 minutes after waking before coffee.
- Caffeine lasts 3 to 7 hours in most adults, so the afternoon cup matters more for sleep.
- Your natural morning cortisol surge arrives within about 45 minutes of waking, coffee or not.
The short answer
Caffeine does raise cortisol. How much depends heavily on whether your body is used to it, and on the time of day. Regular coffee drinkers build up partial tolerance, and the study that shows this most clearly is also the one that complicates the popular morning advice.[14]
Inside the main study
Researchers recruited 96 healthy adults who normally drank caffeine. Each spent a week at a time on placebo, 300 mg a day or 600 mg a day, then came in for a test day with three large doses at 9 am, 1 pm and 6 pm. Saliva cortisol was sampled eight times between 7:30 am and 7 pm.[14]
table · what happened on test day
| The week before | 9 am dose | Afternoon doses |
|---|---|---|
| No caffeine (placebo) | Cortisol rose | Cortisol stayed higher all day |
| 300 mg a day | No rise | Cortisol rose again from 1 pm to 7 pm |
| 600 mg a day | No rise | Smaller rise, but still present |
The authors’ summary was that cortisol responses to caffeine are reduced in regular users, but not eliminated.[14]
Morning cup, afternoon cup
Two details stand out. First, cortisol before the first coffee, at 7:30 am, barely differed whatever people had been drinking that week. Second, in habitual drinkers, the morning dose was the one that did nothing to cortisol. The later ones still did.[14]
The test-day doses were large, 250 mg each, and the volunteers were young and healthy. So treat the pattern as a guide, not a rule for your exact cup.
The 90-minute rule
The trend says to wait 90 minutes after waking so coffee does not “stack” on your natural morning peak. Cortisol does climb early: the steepest part comes within about three quarters of an hour of opening your eyes[10] and peaks around half past eight in people on a typical schedule.[8]
What we could not find is a study testing the rule itself. No trial we know of compared coffee at waking with coffee 90 minutes later and measured cortisol, energy or sleep. And in the main study above, the morning cup in regular drinkers did not raise cortisol at all. If waiting suits you, there is no harm in it. It is a preference, not a finding.
What matters more
For most people the bigger question is the other end of the day. Half of a dose is typically still circulating 3 to 7 hours later, and clearance slows further in pregnancy or with oral contraceptives.[26] A large 400 mg dose still cut into sleep in one study when it was swallowed 6 hours before lights out.[13]
- Set a cut-off. The caffeine calculator estimates your personal cut-off time.
- Watch the 3 pm habit. It is the cup most likely to touch both cortisol and sleep.
- Curious about tea’s pairing? Read L-theanine and caffeine.
Keep your coffee. Lose the myths.
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Sources
- Lovallo et al., 2005. Caffeine stimulation of cortisol secretion across the waking hours in relation to caffeine intake levels. Psychosomatic Medicine.
- Stalder et al., 2016. Assessment of the cortisol awakening response: Expert consensus guidelines. Psychoneuroendocrinology.
- Chan & Debono, 2010. Replication of cortisol circadian rhythm: new advances in hydrocortisone replacement therapy. Therapeutic Advances in Endocrinology and Metabolism.
- Temple et al., 2017. The Safety of Ingested Caffeine: A Comprehensive Review. Frontiers in Psychiatry.
- Drake et al., 2013. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine.
This article is educational and isn’t medical advice. It was written and checked by the UNWIRE™ editorial team; no clinician has reviewed it yet. UNWIRE™ is a nutrition company, and this article does not describe any product.
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