Caffeine addiction is a mild addiction to the drug caffeine,
which occurs naturally in tea, coffee, Yerba mate, and other
sources, and which is added to some soft drinks and medications.
Although it shares some things in common with other addictions,
caffeine addiction is a much milder addiction than that to "harder"
stimulant drugs like cocaine and amphetamine.
Caffeine addiction is characterized by unpleasant, but
relatively mild withdrawal symptoms when a person stops using
caffeine. These include headache, fatigue, and trouble
concentrating, among other things. Caffeine withdrawal is usually
relatively mild and the worst of it is gone after a few days.