This article is from the WebMD Feature Archive

If you crave caffeine to get you through the day, you're not alone. About 68% of Americans say they're hooked on coffee this year, compared with 64% last year, according to the National Coffee Association.

Sales of caffeine-laced energy drinks such as Red Bull and Monster are expected to rise 60% this year, says Gary Hemphill of the Beverage Marketing Corporation, a consulting firm in New York.

If those don't give you enough of a buzz, you can turn to sodas, coffee-flavored yogurt -- some of it has as much caffeine as a 12-ounce soda -- coffee ice cream, chocolate candy, or iced tea.

And one new product, controversially named Cocaine, goes one step further, offering a mega-dose of caffeine that dwarfs its nearest competitors.

Some medicines and dietary supplements for weight lossweight loss also include a dose of caffeine. Coke is even planning to roll out a new "negative calorie" carbonated green tea beverage this fall called Enviga that combines caffeine with other ingredients to -- according to the company -- increase calorie burning.

So what's the harm, ask caffeine fans, who point to studies showing the benefits of caffeine, such as boosting memory and improving concentration and perhaps lowering risks of diseases such as Alzheimer's and liver cancerliver cancer.

But others are alarmed by what they say is an increasingly overcaffeinated nation; they are concerned by studies finding too much caffeine can set you up for high blood pressurehigh blood pressure, high blood sugar, and decreased bone densitybone density -- not to mention jangled nerves.

Caffeine abuse by young people alarms some experts. It was the cause of many calls to an Illinois Poison Center over a three-year tracking period, a team of doctors reported at the American College of Emergency Physicians annual meeting in New Orleans.

How Caffeine Works

"Caffeine exaggerates the stress response," says James D. Lane, PhD, professor of medical psychology at Duke University Medical Center in Durham, N.C., and a long-time caffeine researcher. "At the cellular level, caffeine locks the receptor normally used by adenosine, a brain modulator that provides feedback to avoid overstimulation of nerve cells. If adenosine is locked up, nothing keeps the nervous system from getting too excited at a cellular level."

People joke about being hooked on caffeine, but is it truly addictive? Researchers have debated that question for years.

"There's no question," says Roland R. Griffiths, PhD, professor in the departments of psychiatry and neuroscience at Johns Hopkins University School of Medicine in Baltimore and a veteran researcher in the area. Caffeine is addictive for some people, he says. "Caffeine does produce dependence, and caffeine withdrawal is a real syndrome."

But George Koob, PhD, professor of the Committee on the Neurobiology of Addictive Disorders at The Scripps Research Institute, San Diego, disagrees. "While it is possible to be addicted, most people are not," he says. "I think most of my colleagues would agree."

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