Strictly speaking, tests of proportions provide full information only when the period at risk for all subjects is the same. With clinical trials, censorship is common. One way of testing for an interaction of treatment group and sleep status is by conducting a stratified log rank test. The researchers will perform the stratified log rank test to examine whether the length of time to MADRS response is the same between sleep groups. A significant chi-square statistic, weighted by size of stratum, would indicate that low dose quetiapine is more effective for those with insomnia.