Does coffee raise cortisol? What the studies found

Does coffee raise cortisol? Not reliably. In one controlled trial of daily coffee drinkers at rest, a cup of coffee did not change salivary cortisol. In other, smaller studies, mostly of athletes or people under stress, caffeine was linked to higher cortisol. The honest answer is that results are mixed and depend on the setting.

The evidence here is thin, so this page is short.

What a controlled trial found

A 2016 trial in Nutrition Journal gave 40 healthy adults aged 20 to 55 four different coffees, one week apart, in random order. All of them were daily coffee drinkers. Each drink was 200 ml and contained 160 mg of caffeine. People fasted for 8 hours first, avoided caffeine, alcohol and exercise the day before, and had saliva collected at 60, 120 and 180 minutes after the drink.

Coffee did not change salivary cortisol, whichever type it was. It did raise blood pressure, within the healthy range, and it raised an enzyme in saliva (salivary alpha-amylase) that the authors take as a sign of sympathetic nervous system activity. They note that earlier studies split, with some agreeing with their result and some not, and that their volunteers were calm and healthy, which may matter (Nutr J, 2016).

That trial also bears on a common question, whether coffee on an empty stomach raises cortisol. The volunteers had fasted for 8 hours, and the study picked people who didn’t usually eat breakfast, so coffee without food was not unusual for them. Cortisol still didn’t change. That is one small trial of one kind of drink, with sugar added, so it doesn’t settle the question.

Where caffeine has been linked to higher cortisol

• After hard exercise. In a 2024 crossover study of 15 male football players, blood cortisol after a sprint test was lowest after a placebo capsule. The paper’s own statistics found no significant difference between caffeinated coffee, decaffeinated coffee and caffeine capsules, although its abstract describes the highest cortisol after caffeinated coffee and caffeine powder (Nutrients, 2024). Exercise itself raises cortisol, and 15 people is a small group.
• In reviews of athletes. A 2021 review of caffeine and other ergogenic aids lists studies pointing both ways: higher salivary cortisol after caffeine in some, no change in others, and a lower level in one study of cyclists. It also lists two studies finding raised salivary cortisol after caffeine in athletes who were sleep deprived. It sums up caffeine studies as reporting either increased cortisol, or a rise in salivary amylase without a cortisol rise (Medicina, 2021).
• Under stress. A 2024 study in BMC Psychology gave 48 men an online stress test and sorted them by coffee habit, none, one to three cups a day or four or more. Average cortisol rose after the test, and the groups did not differ (BMC Psychol, 2024). The authors cite earlier work finding that caffeine raised cortisol only when combined with mental stress.

Taken together: the sources don’t show that a normal cup of coffee reliably raises cortisol in a rested, healthy person, and they do show that caffeine plus stress or hard exercise can look different. None of the sources followed people over years to see whether a coffee habit changes cortisol patterns.

Coffee and a cortisol test

MedlinePlus says stress, exercise, pregnancy, hot and cold temperatures and some medicines, such as birth control pills, can change cortisol results. Caffeine is not on its list. That is not a statement that caffeine has no effect, only that it isn’t listed. Follow the instructions on your lab order, and ask the person who ordered the test if you’re unsure. See AM and PM timing.

Caffeine, sleep and anxiety

Caffeine matters for the symptoms people link to cortisol. MedlinePlus lists caffeine among the substances that can cause chronic insomnia, and says caffeine, other substances and certain medicines can make anxiety symptoms worse. Those effects don’t depend on any cortisol change. See cortisol and sleep and cortisol and anxiety.

When to see a clinician

If you have a racing heartbeat, anxiety, trouble sleeping or tiredness that you think is linked to caffeine, a clinician can look at all the possible causes. A cortisol result alone won’t answer it. Persistent symptoms with signs of a hormone problem are also worth raising. For too much cortisol, they include easy bruising, wide purple stretch marks and weak muscles (high cortisol). For too little, they include long-lasting fatigue, weight loss and loss of appetite (low cortisol).

If you take a steroid medicine, don’t change it because of anything here. Ask your prescriber.