This study will examine the biological factors that may modulate the relationship between
depression and the development of Alzheimer's disease (AD). Since the direction of causation
between depression and the biological factors associated with AD is unknown, the only way to
understand cause and associated risk is to treat the depressive symptoms and examine the
effects on AD biomarkers. The study involves an FDA-approved treatment for major depressive
disorder. It will compare the SSRI antidepressant escitalopram with placebo. The hypothesis
is that a reduction in depressive symptoms will be associated with a normalization of CSF AD
biomarkers as well as peripheral inflammatory markers. This research would contribute to
fundamental knowledge about potentially modifiable risks of Alzheimer's disease (AD).