Hypothesis 2: Is high-dose quetiapine (150 - 300 mg/day) more effective for patients presenting with melancholic depression at treatment baseline? To test this hypothesis the researchers are using data from D1448C00001 (150mg, 300mg, and placebo arms only; Weisler et al., 2009), D1448C00002 (150mg, 300mg, and placebo arms only, excluding duloxetine arm; Cutler et al., 2009), D1448C00003 (quetiapine and placebo arms; Bortnick et al., 2011), and D1448C00004 (quetiapine and placebo arms only, excluding escitalopram; Wang et al., 2012) in order to conduct a pooled analysis. A pooled analysis is preferred as the researchers will then have enough statistical power to detect a subgroup interaction (see analysis plan below). This pooled analysis would include data from 1570 participants (n = 935 for quetiapine 150 mg/day; n = 635 for placebo).