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In our fast-paced times, people often need some chemical assistance to keep up. For 90% of people in the English-speaking world, that stimulant chemical is caffeine. Here are ten surprising facts and myths about the world's most commonly used drug.

Caffeine is the world's most commonly used stimulant drug. Once largely confined to coffee, tea, and cola drinks, caffeine is now appearing in places where it is least expected. Energy drinks often pack a punch with up to 8 times as much caffeine per serving as in a cup of coffee, and caffeine even appears in potato chips, candy bars, chocolates, and bottled water. For a quick jolt of high-dose caffeine, in much of the world the beverage of choice is Red Bull, but chocolate-covered coffee beans are almost as stimulative.

The average person in Europe or North America consumes the caffeine equivalent of about three cups of coffee a day, or 200 to 250 mg of caffeine daily. A single can of Red Bull contains up to 300 mg of caffeine, however, and some people in the EU and US drink (usually as energy drinks) or eat (usually as chocolate covered coffee beans) up to 3000 mg of caffeine each and every day.

Excessive consumption of caffeine causes some surprising side effects. Here are five surprising facts about the side effects of drinking too much coffee, cola, or tea, or downing too many energy drinks.

Caffeine Fact No. 1. Excessive consumption of caffeine can induce hallucinations.

You don't really trip out on coffee the way you might trip out on LSD, but excessive consumption of caffeine from energy source can make you see things that are not there. Usually this effect kicks in after the seventh or eighth cup of coffee in a single day or the second or third energy drink in a single hour. Consuming more than about 300 mg of caffeine before the liver has time to detoxify it can cause you to see, hear, smell, feel, or even taste things that are not there. This side effect is linked to the release of the stress hormone cortisol and is worst during times of emotional, although not physical, stress.

Caffeine Fact No. 2. Paradoxically, consumption of large amounts of caffeine during stress can cause some people to mellow out.

Caffeine, researchers recently have discovered, can activate the same receptors in the brain that respond to tetrahydrocannabinol (THC), the psychoactive chemical in marijuana. In small doses caffeine stimulates both the A1 and A2A receptors of the striatum of the brain. Activated A1 receptors cause you to "mellow out," while A2A receptors cause you to "stress out." In large doses caffeine stimulates the A1 receptors more than it stimulates A2A receptors so the net effect is relaxation and a feeling of security.

Caffeine Fact No. 3. Consuming caffeine interferes with your ability to learn some facts, but enhances your ability to learn others.

Caffeine stimulates almost all of the regions of your brain. Whether that helps or hinders your ability to learn new information depends on an interaction with another brain chemical called dopamine. Rewarding behaviors induce the brain to release dopamine. When you dislike the information you are trying to learn, your brain doesn't produce as much dopamine, and caffeine simply interferes with your ability to focus on the task at hand. When you like the information you are trying to learn, your brain produces more dopamine, and caffeine heightens your brain's ability to focus on your assignment. Just don't drink so much coffee that you start hallucinating your homework.

Caffeine Fact No. 4. Caffeine enhances your sensibilities but dulls your senses.

Neurologists have found that caffeine enhances the retention of verbal and factual memories, but it interferes with the brain's ability to record feelings and perceptions. You may be able to articulate an explanation of your experience better when you have had an energy drink, but you will be less able to remember how you feel. This isn't necessarily a bad thing for students, but it would be important to be able to feel the same way both when studying and when taking a test--or caffeine would diminish academic performance.

Caffeine Fact No. 5. Caffeine consumption encourages risky behaviors.

The thrill of sex, gambling, drinking alcohol, eating delicious food, listening to beautiful music, stealing, or taking physical risks releases dopamine in the brain. Caffeine enhances the brain's ability to respond to dopamine, and makes these risky and potentially addictive behaviors even more risky and even more potentially addictive. On the other hand, caffeine makes it easier to get a thrill when not performing risky behaviors. Nearly every Alcoholics Anonymous meeting occurs around a coffee bar, which enhances good feelings that don't have to be induced by drink.

Continue reading after recommendations

  • Childs E, de Wit H. Subjective, behavioral, and physiological effects of acute caffeine in light, nondependent caffeine users. Psychopharmacology. 2006. 185(4):514–523.
  • Scoley A, Kennedy D. Cognitive and physiological effects of an “energy drink: an evaluation of the whole drink and of glucose, caffeine and herbal flavouring fractions. Psychopharmacology. 2004.176:320–330