Milhorn , 1990 . Tolerance occurs with continued use , wherein the individual must take more and more of the drug to achieve the same effect . When drug use is discontinued , withdrawal occurs the person experiences unpleasant physical and psychological reactions . Drug dependence also make the individual take more of the drug than intended , tries to control use but can 't and spends a great deal of time trying to obtain the drug . The degree to which tolerance develops and the severity of...











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