2. History of suicidal ideation within 3 months prior to Day 1 or an episode of severe depression within 3 months prior to Day 1. Severe depression is defined as any episode of depression that requires hospitalization, or the initiation of antidepressant therapy, or an increase in the dose of an existing regimen of antidepressant therapy. NOTE: Subjects receiving ongoing antidepressant therapy are not excluded from the study unless the dose has been increased within the 3 months prior to the Screening Visit.