For 50% of people, that signal is a headache.

Choksi says those who don't get their caffeine will often experience flu-like symptoms, anxiety, irritability, and disphoria, just as in any withdrawal disorder. Others feel fatigued, drowsy, have difficulty concentrating, and may go as far as nausea, vomiting and muscle pains. Check, check, and check, say several people who were asked recently outside of Starbucks how they feel without their caffeine.

High school senior Kevin Polosky said he averages two carbonated drinks and three cups of coffee per day. Without it, he feels tired.

"I depend on it to stay awake," he said, adding that when he wants to stay up late and have fun on the weekends, he throws in a two-liter bottle of Mountain Dew MDX.

"Tired and grumpy," said his friend Matt Truax, a fellow senior who hits Starbucks three times a day.

Mary Devereaux said she never goes without her one or two cups of coffee per day.

"The longest I've gone without was this morning. I got up at 6:30 and it was 9:20 before I got it. And I felt crappy," she said with a laugh. "I would be a victim of withdrawal."

IS IT AN ADDICTION
Devereaux's one or two cups is hardly an addiction, is it?

Yes, says Choksi. As little as one cup of coffee a day can be an addiction if your body experiences withdrawal symptoms without it.

Results of a Johns Hopkins study published in 2004 recommend caffeine withdrawal be included in the next edition of the Diagnostic and Statistical Manual of Mental Disorders.

Researchers identified the withdrawal symptoms cited by Choksi and added that 13% of those in the study had clinically significant distress or functional impairment incompatible with working.

Typically, they said, onset of symptoms occurred 12 to 24 hours after stopping caffeine, with peak intensity between one and two days. Those feelings of withdrawal can last for up to 10 days. Abstinence from doses as low as 100mg of caffeine per day, or about one small cup of coffee, sometimes produced symptoms.

The research also showed that avoidance of caffeine withdrawal symptoms motivates regular use of caffeine.

What happens when one gives up caffeine, and why would anyone want to? Choksi cites changes in the brain's blood circulation and a release of neurochemicals that causes withdrawal symptoms.

"I'm sure there is a significant psychological overlay, too, as with all addictions," he said. "To say this is purely physiological would be to say it is out of a person's hands."

WHY QUIT?
As to the why of quitting caffeine, Choksi cites many health reasons, including people with heart problems.

One patient early in his practice, he said, complained of being nervous, shaky, sweaty, and depressed. He had huge mood swings and couldn't sleep. His antidepressants and anti-anxiety medications were not working when he was referred to Choksi.

Choksi asked the man, a cabdriver, how much caffeine he was getting each day. The list included two pots of coffee before he left the house in the morning, a 24-pack of cola, many refills of his coffee travel mug and a pot with dinner.

"After that, I got in the habit of asking every patient how much caffeine they drink," he said.

Caffeine addiction can make some people seem manic, he added, and symptoms of manic behavior can affect jobs and families. To someone with an anxiety or mental disorder, drinking caffeine "is like pouring gasoline on a fire," he said.

The cabdriver was able to gradually cut down his intake and get off medication altogether. Choksi says he used a gentle approach, substituting decaffeinated products gradually, but that 50% of us can quit at once without getting headaches.

"Sometimes simple common sense and awareness will help take care of caffeine intake," said Choksi. "Some people can quit cold turkey and some can cut down to half and be fine. We have to figure out what works best for us."

From the May 9, 2007, Prepared Foods e-Flash