For some, the day doesn’t begin until the first cup of coffee. But for others, that ritual—famous for bringing focus and energy—can cause a racing heart, jittery hands, and a vague sense of dread that lingers long after the caffeine buzz fades.
Here’s why caffeine can trigger anxiety, what caffeine does inside the body, and why some people are far more sensitive to it than others.
Within 15 to 45 minutes of drinking a cup of coffee, caffeine travels through the bloodstream and reaches the brain. There, it blocks adenosine receptors, the neural “brakes” that help promote calm and drowsiness. This blockade leads to the release of dopamine and norepinephrine: two neurotransmitters that drive “heightened alertness, increased arousal, and reduced fatigue,” says Dr. Amin Yehya, a cardiologist at Sentara Health in Virginia. But in higher amounts, dopamine and norepinephrine also raise heart rate and blood pressure and activate brain regions involved in threat perception. It’s the same system that drives the body’s stress response and can contribute to restlessness and a racing mind.
Dr. John Higgins, a cardiologist at UTHealth Houston, notes that caffeine’s most immediate effects are neurological. When caffeine blocks adenosine receptors and “removes that brake, neurons fire faster, cortical arousal increases, and blood vessels constrict slightly, raising blood pressure and creating physical sensations many people interpret as nervousness.”
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This sudden state of activation can feel like clarity and motivation for some—and like anxiety for others. A 2023 study published in the journal Clinical Autonomic Research shows that this heightened arousal can mimic anxiety’s physical symptoms almost perfectly, which helps explain why the line between “energized” and “uneasy” is so thin.
Caffeine can also trigger anxiety through another pathway. It activates the hypothalamic-pituitary-adrenal (HPA) axis, increasing cortisol and adrenaline, which are the body’s core stress hormones. “Caffeine stimulates the same hormonal pathways that activate during stress,” Yehya says.
Kevin Woods, director of science at Brain.fm, says that caffeine’s promise of sharper focus can be misleading. “Your prefrontal cortex, where focus and decision-making happen, doesn’t actually work better in fight-or-flight mode,” he says. “You might feel wired, but that’s not the same as being mentally sharp.”
Not everyone feels anxious after drinking coffee, and genetics play a role in determining who does.
Variations in genes alter how the brain’s adenosine and dopamine receptors function, Yehya says, while certain mutations can slow caffeine metabolism in the liver. People with these gene variants process caffeine more slowly, allowing it to linger in the bloodstream and prolonging its stimulating effects, which can contribute to feeling more anxiety.
This is why “the same cup of coffee can feel totally different from one person to another,” Higgins says.
The U.S. Food and Drug Administration recommends no more than 400 mg of caffeine per day—about two to three 12-oz. cups of brewed coffee—for most healthy adults. But that limit isn’t hard and fast. “There is no designated amount of caffeine that universally triggers anxiety,” Yehya says.
Genes aren’t the only factor. So are a person’s caffeine tolerance and underlying health, says Dr. Ajay Pillai, an electrophysiologist at VCU Health Pauley Heart Center. “Caffeine intake may acutely raise heart rate and blood pressure by as much as 5 to 10 mmHg,” he says. “This effect may be more pronounced in people with hypertension or those already under stress.”
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For sensitive people, even one cup can be too much, while others can tolerate more without ill effects. “Know your body and limit intake,” advises Dr. Mohanakrishnan Sathyamoorthy, chair of internal medicine at Texas Christian University’s Burnett School of Medicine. “Be mild to moderate in use, and be knowledgeable about the caffeine dose in your favorite drinks.”
Sleep deprivation, chronic stress, and hormonal fluctuations can all amplify caffeine’s effects. “When the body is already under stress, caffeine can compound that response,” says Dr. Sogol Ash, a functional and preventative medicine doctor and medical advisor to the vitamin patch company, Barrière. “Poor sleep, hormonal fluctuations, and anxiety elevate baseline levels of cortisol and adrenaline, leaving the nervous system in a heightened state.” Add in caffeine, and the effects can feel stronger.
A lack of sleep fundamentally changes how caffeine interacts with the brain.
“When you’re running on empty, your prefrontal cortex is already compromised,” Woods says. “Caffeine creates the illusion of alertness without restoring actual cognitive function. You might feel awake, but your ability to concentrate remains impaired.”
Women taking hormonal contraceptives or who are pregnant may also metabolize caffeine more slowly.
The good news is you don’t have to quit coffee altogether. “Moderate coffee intake—about two to three cups per day—is generally safe,” Yehya says. Timing matters, though. Avoiding caffeine in the afternoon or evening helps protect sleep quality, which directly affects next-day anxiety.
Also, never drink coffee on an empty stomach, Ash suggests. “Food helps slow absorption of caffeine and softens its impact on stress hormones,” she says. Pairing coffee with breakfast or milk-based foods can blunt spikes in cortisol and blood sugar. For those looking to reduce caffeine’s punch, switching to half-caf, smaller servings, or decaf can help.
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The preparation method matters less than you might think, says Higgins.
Espresso packs the most caffeine per ounce (about 63 mg per shot), but an 8-oz. cup of coffee typically delivers more total caffeine—around 95 mg.
Cold brew and hot brew deliver similar caffeine amounts when matched for coffee-to-water ratios, Higgins says. “The myth that cold brew is stronger comes from concentrate preparations, which use higher coffee-to-water ratios,” he says. “Dilute it properly, and the caffeine content normalizes.”
Woods also encourages working with your body’s natural rhythm. “Your cortisol naturally peaks around eight or nine in the morning, so waiting until mid-morning when it dips allows caffeine to complement your natural rhythm,” he says.
If you experience anxiety, palpitations, or insomnia with moderate coffee consumption, it might be time to re-evaluate your caffeine habit. “If someone’s anxiety persists despite changes in caffeine intake—or their symptoms impair daily functioning—other medical conditions should be considered,” Yehya says. That could include anxiety disorders, cardiac arrhythmias, or thyroid issues.
Caffeine-related anxiety is common and manageable, but it can also be a clue about something deeper. “Speak to your physician and include caffeine use as part of your health history,” Sathyamoorthy says. “It’s an easy thing to overlook, but it can be an important piece of the puzzle.”
Ultimately, the answer isn’t necessarily to give up coffee entirely but to understand your body’s relationship with it. For some, that means switching to decaf; for others, it means adjusting timing, food, or amount. “Caffeine isn’t the enemy,” Woods says. “The goal is working with your brain instead of against it.”
