Their study shows no difference in withdrawal symptoms based on the source of caffeine, which includes coffee and sodas, some teas, chocolate, and medications such as Excedrin and NoDoz. 'It shows very nicely that the effects of caffeine withdrawal are consistent, that several symptoms are of large magnitude, and that a minority of people cannot perform daily functions when they go without caffeine,' he tells WebMD. This study, co-authored by American University researcher Laura Juliano, PhD, does that, says Hughes. 'Not only do you have to show it produces symptoms, but you have to show that those symptoms can interfere with daily function.'

'Caffeine withdrawal was proposed for DSM-IV, but the major objection to including it as a disorder was an absence of good data showing clinical significance,' says Hughes, who was not involved in Griffiths' study.

That's key for inclusion in the DSM, says John Hughes, MD, a University of Vermont psychiatrist and addiction specialist who serves as a medical consultant for the book. 'The withdrawal symptoms can be mild or severe, but it's estimated that 13 percent of people develop symptoms so significant that they can't do what they normally would do - they can't work, they can't leave the house, they can't function,' he says. 'The duration is between two and nine days.'Ī new revelation in Griffith's analysis may be what upgrades caffeine withdrawal from its current 'more study is needed' status to 'disorder' status: These withdrawal symptoms are severe enough in about one in eight people to interfere with their ability to function on a day-to-day basis. 'Onset of these symptoms typically occurs within 12 to 24 hours of stopping caffeine and peaks one to two days after stopping,' Griffiths tells WebMD.

Flu-like symptoms such as nausea, vomiting, muscle pain, and stiffness.

'Unhappy' mood, depression, or irritability.

Headache, the most common symptom, which affects at least of 50 percent of people in caffeine withdrawal.

Griffiths' analysis shows as little as one cup of coffee can cause an addiction, and withdrawal from caffeine produces any of five clusters of symptoms in some people:

Length of caffeine withdrawal symptoms