Research has shown that drinking just 100 milligrams of caffeine a day is enough to develop a dependence and trigger withdrawal symptoms. The escape from the clutches of withdrawal is a big part of what makes the day’s first cup of coffee so wonderful. “Feeding that dependence feels really good,” Juliano says. The implication: The positive feelings we associate with drinking coffee don’t represent a net gain in energy or alertness; they’re really the result of withdrawal maintenance.