The purpose of this study is to verify the progression delaying effect of escitalopram in Alzheimer's disease using volumetric MRI change as a primary outcome measure.

• Study institutions: Four university hospitals in Korea
• Design:52 week, randomized, placebo-controlled, double-blind, parallel group design
• Subjects:80 probable Alzheimer's disease patients who have been taking donepezil at stable dose for at least 2 months (Escitalopram 40 : Placebo 40)

• Drug: escitalopram
• Drug: placebo

• Experimental: escitalopram 20mg
• Placebo Comparator: Placebo

Inclusion Criteria:

• Age:40~90 years
• Education:not illiterate
• Clinical Dementia Rating (CDR):0.5~2
• Modified Hachinski Ischemic Score (Rosen et al., 1979):less than 4
• Dementia according to DSM-IV criteria
• Probable Alzheimer's disease according to NINCDS-ADRDA criteria
• Current ongoing donepezil medication at stable doses (5 ~ 10 mg/day) for at least 2 months

Exclusion criteria:

• Evidence of delirium, confusion or altered consciousness
• Evidence of Parkinson's disease, stroke, brain tumor and normal pressure hydrocephalus
• Evidence of infectious or inflammatory brain disease
• Evidence of serious cerebrovascular diseases
• Current major depressive disorder or other major psychiatric illnesses
• Evidence of serious or unstable medical illnesses which can significantly change cognitive state
• History of alcohol or other substance dependence
• Any antidepressant medications within the previous 4 weeks
• Absence of a reliable and cooperative collateral informant
• Any conditions which prohibit MRI scan, such as presence of pacemaker or cerebrovascular clip, and claustrophobia