Methamphetamine has medical uses as well as the potential to cause addiction. Methamphetamine addiction typically occurs when a person begins to use the drug as a stimulant, for its powerful enhancing effects on sex, mood and energy, alertness and ability to concentrate, and weight loss and appetite suppression, among its other psychological and physical effects.
Over time tolerance develops, and users have greater difficulty functioning and experiencing pleasure than they did before, which persists indefinitely due to neurotoxicity produced by methamphetamine in long-term recovered addicts.