In the treatment of depression, the role of sleep is important as there are mutual relationships between mood disorder and sleep disorders. Over 80% of major depressive disorder (MDD) patients report sleeping problems. Depression can strongly impair cognitive functioning and daytime alertness. (Mirtazapine (Remeron) is an antidepressant and sleep-promoting agent that has been available in Canada for a few years. However, research investigating the effects of mirtazapine on sleep is limited and it is not known what are the short- and long-term changes in sleep architecture associated with this drug and if daytime performance is affected.