No, there isn't a withdrawal effect from everything. Caffeine is clinically proven to be addictive. It raises your risk of heart attack and stroke. It increases your odds of getting ulcers. It dehydrates you. It can contribute to kidney stones. It affects the absorption rates of countless medications. It depresses cognition, as soon as the initial bump wears off. It causes drug dependence. It causes insomnia and irritability. [i][u]It is classified as a psychoactive substance[/u][/i]. 10 grams in a day is enough to kill any healthy adult. 10 grams of cannabis will just leave you derpy, for a few hours.