This study is a double-blind, randomized, placebo-controlled, parallel group study. The study consists of two groups of subjects with major depression treated for ten weeks with a common antidepressant regimen, 20-40 mg of fluoxetine hydrochloride per day; and randomized to receive (in addition) either eszopiclone 3 mg or placebo for eight weeks. This study was previously posted by Sepracor Inc. In October 2009, Sepracor Inc. was acquired by Dainippon Sumitomo Pharma., and in October 2010, Sepracor Inc's name was changed to Sunovion Pharmaceuticals Inc.