This is a study of nontreatment seeking individuals who use MA compared to individuals who do not use MA(control participants). The study has three goals: 1. it aims to identify the brain regions and pathways that may contribute to the problems of MA abusers in performing mental tasks; 2. it will serve as a double-blind, placebocontrolled,within-subjects study to determine the safety and tolerability, and positive effects of MA in MA-abusing volunteers treated with atomoxetine or placebo; 3. It aims to compare the brain activity as measured by structuraland functional magnetic resonance imaging (fMRI). These are noninvasive brain imaging procedures, that will be used to study brain function while control and MA using participants take atomoxetine or placebo and perform tests of memory and concentration.