Therefore, studying placebo effects offers a window into the functioning of the neural circuits that are disturbed in MDD and improve with effective treatment. The goals of this study are to determine whether expectancy affects the outcome of antidepressant pharmacotherapy and to investigate the neural mechanisms of expectancy effects. These will be accomplished by conducting a clinical trial randomizing adult outpatients with MDD to 8 weeks of treatment in high vs. low expectancy conditions. The high expectancy condition will be open administration of citalopram, while the low expectancy condition will be placebo-controlled administration of citalopram. The neural mechanisms of expectancy will be determined using functional Magnetic Resonance Imaging (fMRI) paradigms to investigate treatment activation differences in brain regions associated with placebo effects and MDD.