Methamphetamine (or meth) is a stimulant. The stimulant creates highly positive feelings in the user when it is first taken into the blood stream and on through the nervous system. When drug's effects wear off however, there is an opposite reaction and "bad feelings" begin to overtake the user. This occurs because the meth suppresses normal levels of adrenaline production in the user. Adrenaline, when being produced at normal levels, keeps the user balanced emotionally and physically. Now, thanks to the meth, the user experiences a chemical imbalance. To the user, the only way to counter this chemical imbalance is to take more and more meth until the "good feeling" return. This cycle represents the nature of meth addiction.