Why does caffeine make some people anxious?

Caffeine is one of the most popular drugs in society today. The ubiquitous stimulant has helped countless people power through late-night revision sessions and early-morning meetings.

Like any other drug, caffeine has side effects that become more prominent as the dose increases. Some people will have experienced anxiety after a couple of cups of tea or coffee.

Why is it that some people feel anxious after consuming caffeine? Does your morning coffee cause or exacerbate anxiety?  Research points to why you might want to limit your daily intake of caffeine.

How caffeine works

In 2008, research appearing in the Journal of Neurochemistry demonstrated the way caffeine works. The drug improves alertness by triggering the release of adrenaline and blocks the chemical that makes you feel sleepy, called adenosine.[1]

Anybody who has been scared at some point knows how it feels to have adrenaline coursing through their veins. When a person drinks too much coffee, the adrenaline it triggers can cause anxiety and jitteriness.

How much you have matters

50 to 200 milligrams (mg) of caffeine is considered a low dose for the average healthy adult. Consuming more than 400mg in one sitting can make someone overstimulated and anxious. A cup of coffee contains around 95mg of caffeine. When a person has more than two cups, they may experience physical and psychological symptoms. [2]

High doses of caffeine may lead to anxiety. In addition, people who suffer from panic attacks or anxiety disorders are susceptible to caffeine side effects. [3] [4]

The other symptoms that caffeine can cause include rapid heart rate, stomach problems, insomnia, restlessness and nervousness.

According to the American Food and Drug Administration (FDA), having 1,200mg of caffeine in a short period can be dangerous. Having this much caffeine may cause seizures and other toxic effects.[5]


For the vast majority of us, caffeine consumption is safe and can even offer benefits. However, for a small portion of people, caffeine consumption may worsen symptoms of pre-existing anxiety. Keeping your daily intake below 400mg can help reduce the chance of experiencing unpleasant side effects.

If you are concerned that your caffeine intake might be causing or increasing your anxiety, speak with your doctor.

  1. Ferré S. An update on the mechanisms of the psychostimulant effects of caffeine. Journal of Neurochemistry [Internet]. 2008 May [cited 2021 Sep 20];105(4):1067–79. Available from: https://pubmed.ncbi.nlm.nih.gov/18088379/
  2. WebMD. Is Caffeine Fueling Your Anxieties? [Internet]. WebMD. WebMD; 2019 [cited 2021 Sep 20]. Available from: https://www.webmd.com/anxiety-panic/news/20190719/is-caffeine-fueling-your-anxieties
  3. Lara DR. Caffeine, Mental Health, and Psychiatric Disorders. Cunha RA, de Mendonça A, editors. Journal of Alzheimer’s Disease [Internet]. 2010 Apr 14 [cited 2021 Sep 20];20(s1):S239–48. Available from: https://pubmed.ncbi.nlm.nih.gov/20164571/
  4. Uma Naidoo, MD. Eating well to help manage anxiety: Your questions answered – Harvard Health [Internet]. Harvard Health. Harvard Health; 2018 [cited 2021 Sep 20]. Available from: https://www.health.harvard.edu/blog/eating-well-to-help-manage-anxiety-your-questions-answered-2018031413460


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