Caffeine alters mood and behavior, and it can also result in
physical dependence, says Roland Griffiths, a professor in the
departments of psychiatry and neuroscience at the Johns Hopkins
School of Medicine. "People are hesitant to think of it as a
drug of addiction because it doesn't have a lot of the health
and adverse social consequences associated with our classic
drugs of addiction, yet the basic mechanisms by which it hooks
people are very much like our classic drugs of addiction," he
says. Most people experience mild to modest withdrawal,
Griffiths says, which is relieved by drinking coffee in the
morning after abstaining from it overnight. Many people say, "'I
really don't get going until I have coffee, [and] then I feel
great.' What they're not recognizing is that if they didn't
consume coffee [at all], they would wake up feeling great,"
Griffiths says. Here are some of the signs of caffeine
withdrawal, which typically appear 12 to 24 hours after
abstaining from coffee.