The Buzz on Caffeine

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A tougher question concerns caffeine's fabled ability to lift mood. Studies since the 1980s have looked into its effect on opiate centers of the brain, hoping for a treatment for depression or alcoholism. But is the high also hype? Certainly, among people new to caffeine, the buzz is real. A caffeine novice can get a kick from as little as 20 mg of caffeine--the equivalent of 1.5 oz. of strong drip coffee. But the average coffee drinker may consume upwards of 300 mg a day, often with no discernible effect on mood. Reason: the body quickly habituates to the chemical and requires ever higher doses to feel anything at all.

"Physical dependence can occur in three days," says Roland Griffiths, a professor of psychiatry and neuroscience at Johns Hopkins University School of Medicine. "Habituation to some of the [stimulating] effects may happen even more rapidly." What passes for a lift, Griffiths warns, may be nothing more than relief from the symptoms of caffeine withdrawal--such as lethargy and headache--which begin after overnight abstinence. The discomfort is probably caused by adenosine-starved brain receptors overreacting when the caffeine is removed and the brain chemical starts flowing again.

What's more, as users chase the caffeine buzz, their intake climbs--sometimes to 1,200 mg a day or more, leading to jitteriness and sleeplessness. Blood pressure may become elevated, and although the increase is not always dramatic, it can be dangerous for people at risk for hypertension or other cardiovascular problems.

The key--no surprise-- is moderation. If you're experiencing all the bad and none of the good of caffeine, cut back. Mixing caffeinated drinks with decaf can make for a comparatively painless detox. When a 20-oz. latte can set you back nearly $4, there's more than one reason to keep the joe under control. --By Jeffrey Kluger. With reporting by Paul Cuadros/ Chapel Hill, N.C., and Charlotte Faltermayer/ New York