The goal of this study is to associate atomoxetine and metabolite drug concentrations with clinical efficacy and the development of any clinical adverse drug reactions and to determine whether clinical outcome (efficacy and ADRs) experienced following drug ingestion are more likely to be seen in patients who manifest CYP2D6 and/or CYP2C19 polymorphism(s). Other indications for pharmacogenetics in patient care, relevance of therapeutic drug monitoring, augmentation strategies and dosage guidelines may be generated from the experience and results of this study.