First the researchers will compare MADRS response rates between participants with depression and insomnia and participants with depression and no insomnia (alternate comparison, high sleep disturbance vs low sleep disturbance) who were randomly assigned to received quetiapine 50 mg/day (Analysis A). The researchers are trying to establish that participants with insomnia had a larger response than those without insomnia, and therefore no comparison against placebo is needed. The outcome of interest will be the presence of a positive MADRS response at any time point after baseline (i.e., Day 4, Week 1, Week 2, Week 4, and Week 6). Although this analysis strategy is not equivalent to a formal interaction test of a subgroup treatment effect, which would inappropriately underpowered in this sample, the researchers feel that it is appropriate to provide preliminary support for a subgroup effect that could be evaluated with future research.