Compliance: Participants receiving 75% of their assigned medication will be considered compliant. The 75% criterion ensures that participants will receive adequate treatment to evaluate the comparative efficacy of atomoxetine and placebo. Outpatient compliance will be monitored through weekly pill counts and subject interviews. Medications will be dispensed on a weekly basis and will only be dispensed after compliance is assessed and all assessments are completed. Inpatient compliance will be monitored through inpatient medication records. If a participant is observed to have a compliance problem, then this will be discussed with the participant and a plan formulated to bring the participant back within the compliance parameter. For outpatients, the plan may include contacting the participant's caretaker or scheduling increased clinic visits. These monitoring procedures have been used in other MPRC studies and have resulted in high levels of compliance. Compliance patterns will be carefully monitored in each treatment group and will be described as part of any presentation of study results.