In general, the more caffeine consumed, the more severe withdrawal symptoms are likely to be, but as little as one standard cup of coffee a day can produce caffeine addiction, according to a Johns Hopkins study that reviewed over 170 years of caffeine withdrawal research.
Results of the Johns Hopkins study may result in caffeine withdrawal being included in the next edition of the Diagnostic and Statistical Manual of Mental Disorders, considered the bible of mental disorders, and the diagnosis may be updated in the World Health Organization's International Statistical Classification of Diseases and Related Health Problems.