With coffee shops abound on State Street, many University of Wisconsin students will admit to a weakness for caffeine, especially around exam time when all-nighters are not only possible, but likely.

Students are huge consumers of caffeine, one of the most widely used drugs in the world.

Entering the terms “caffeine” and “college students” on the Google webpage produces 28,000 hits.

Roland Griffiths, a caffeine researcher at the Johns Hopkins School of Medicine, recently released a vast survey of caffeine-withdrawal research. The survey shows for caffeine addicts, missing just one cup of coffee — with an estimated 100 milligrams of caffeine — is enough to trigger irritating withdrawal symptoms such as severe headaches and fatigue.

Caffeine is legal, safe and regularly consumed by 80 percent of Americans, according to the Milwaukee Journal Sentinel. A University of Florida site dedicated to caffeine states while drug experts do not classify caffeine as physically addictive, many believe it is psychologically addictive, as people respond to stress by drinking coffee.

“The general consensus among scientists is that coffee is perfectly safe as long as it is consumed in moderation. A healthy amount of consumption per day is considered to be equal to two-to-three 8-ounce cups of brewed coffee,” according to the site.

The drug’s effects wear off after 12-24 hours, which might explain why many people crave caffeine at particular times of the day, as their consumption patterns become fixed.

Jill DeRose, an employee at Espresso Royale on State Street and a UW junior, said she has noticed regulars at the coffee shop, but believes college students’ schedules determine how often they purchase coffee.

“I’d venture to say it’s not so much the caffeine as the class schedules,” she said. “We do have one regular who comes in every morning and then again eight hours later. Students come in to get their fix in the morning.”

Tony Fettes, who has worked at Steep and Brew for two years, agreed UW students tend to get coffee whenever their busy schedules allow it.

“It could be both,” he said, noting he consumes his fair share of caffeine on the job. “But I think it’s more their daily schedule and routine than the caffeine.”

Hannah Lawler, a UW sophomore and Starbucks employee, said the pattern of coffee consumption differs between the Starbucks where she worked at home and the one on State Street in Madison.

“When I worked at home usually people would come in in the morning or after work enough where you’d know what they were ordering,” Lawler said. “That was usually an older crowd more than teenagers or college students. College students are not as reliable a source because their schedules vary.”

Lawler added, however, she does recognize many of the student Starbucks patrons.

The amount of caffeine in beverages differs by venue, Lawler said, adding Starbucks beverages are higher than average in caffeine content.

Fettes was unsure of the exact amount of caffeine in the Steep and Brew coffees, but he said one shot of espresso is equivalent to a cup of coffee.

“If you get a double shot latte it’s like getting two cups of coffee,” he said.

DeRose said the coffee at Espresso Royale is slightly less caffeinated than many places.

“We tend to have darker roasts,” she explained, noting Espresso Royale offers “eight or nine different roasts.”

Although caffeine addiction has not proven harmful to humans, it does affect behavior. Researchers such as Griffiths believe studying caffeine addiction provides insight into addictive behavior in general.