Mark Nicholson considers himself a recovered drug addict of sorts. His addiction?
"Coca-Cola," he says.
Or more precisely, the caffeine spike in every can. The 51-year-old Idlewylde nurse spent years stashing sodas in his car, in his hospital locker, even by his bed. It was frequently the last thing he drank at night, the first when he awoke.
If he didn't get his fix, he paid: "I'd get this humongous headache and feel like I was going to throw up."
Nicholson ultimately kicked the caffeine habit with help from a little-known Johns Hopkins Hospital program for people hooked on the drug.
But latte lovers, chocoholics and other caffeine junkies take heed: While this guy's case may sound extreme, mounting scientific evidence shows that jokes about caffeine withdrawal are no joke at all - and it doesn't take much to get hooked.
"Some people say it's all in your head," says Roland Griffiths, a caffeine researcher at the Johns Hopkins School of Medicine. "We're able to show, based on a number of rigorous studies, that it's real and biological."
In the most comprehensive survey of caffeine withdrawal research to date, Griffiths and a colleague pored over 170 years of studies and concluded that one small cup of coffee - only 100 milligrams of caffeine - is all it takes to trigger symptoms that include headaches, fatigue and irritability.
For serious caffeine junkies, going cold turkey can be even more traumatic. The latest analysis, published last month in the journal Psychopharmacology, found that some experience flulike symptoms such as muscle pain, nausea and vomiting when they go off caffeine. Thirteen percent of people weathering withdrawal have to call off work or cancel daily chores.
Some psychologists are even pushing the American Psychiatric Association to classify caffeine withdrawal as a bona fide mental disorder in the next edition of its Diagnostic and Statistical Manual of Mental Disorders.
If that happens, it will likely be due in part to Griffiths.
The 58-year-old psychologist is regarded as one of the country's leading investigators of caffeine and its effects. His compact, tidy office on Hopkins' Bayview campus is a playful shrine to his subject - its walls decorated with vintage Coke ads, a plaque-mounted Hershey bar, and a cartoon about the caffeine-addled adventures of "Too Much Coffee Man."
Legal and generally safe, caffeine is the most popular mind-altering drug in the world, consumed by 80 percent of Americans. That fact alone made it worth investigating, says Griffiths, who became interested in the drug in the 1980s.
As a researcher who also studies nicotine, cocaine and other, often-abused drugs, he also realized that caffeine might be a good model for analyzing the addiction process. "It's not cocaine," Griffiths explains. Yet "it controls behavior."
Just how much remains hotly debated. The American Psychiatric Association doesn't recognize caffeine as a drug that causes dependence. But Griffiths says anybody who requires convincing need only hang out at a Starbucks some morning - as Griffiths has done - to watch the regulars roll in like clockwork.
"People get dependent on caffeine," says Griffiths. "The question is: How does the drug do that? What kind of biological mechanism is it hijacking? It becomes this really interesting puzzle to figure out what's going on."
Scientists puzzled over caffeine long before they even knew what it was.
As coffee, tea and chocolate began crossing oceans and continents in the 16th century, Europeans marveled at how these products boosted alertness and stimulated the appetite. A Welsh judge named Walter Rumsey boasted of coffee's "power to cure drunkards," which helped perpetuate a fallacy about caffeine and sobriety that continues today. (Until your liver metabolizes the alcohol, coffee just makes you an alert drunk.)
But caffeinated drinks also drew suspicion early on. In 1635, German physician Simon Pauli cautioned that men who drank coffee or tea risked, as he indelicately put it, "effeminacy and impotence."
Around the same time, an English missionary and chocoholic named Thomas Gage was among the first to note symptoms of caffeine withdrawal. When he skipped one of his habitual four to five daily cups of hot chocolate, Gage reported, "I presently found my stomach fainty."
It wasn't until 1819 that a young German doctor named Friedlieb Ferdinand Runge isolated a bitter-tasting, white powder from coffee. The substance - caffeine - was later found in tea, cocoa pods, cola nuts and nearly 60 other plant species. (Its name derives from kaffee, German for coffee.)
Although scientists have learned much about the drug since then, they still don't know precisely how it produces feelings of well-being, alertness and its other well-known effects. However, recent evidence suggests caffeine may be plugging brain receptors for adenosine, a chemical that causes drowsiness, dilates blood vessels and slows the heartbeat.