This study will investigate the additional benefits of light and ion therapy as added treatments to an antidepressant (fluoxetine) in subjects with major depressive disorder (MDD), versus treatment with fluoxetine alone. Outcomes will include depressive symptom rating scales and measures of quality of life, work absence and productivity, and use of health care services. The primary hypotheses are that, in patients with nonseasonal major depressive disorder (MDD) of at least moderate severity: 1) bright light therapy or negative ion therapy will be superior to a placebo condition in reducing symptoms of depression, and 2) the combination of fluoxetine and either bright light or negative ion therapy is more effective than either monotherapy condition.