Escitalopram Effects on CSF Amyloid Beta

The investigators will measure CSF Amyloid Beta levels before and after two weeks or eight weeks of treatment with escitalopram using a double blind placebo-controlled study design with approximately 30 cognitively normal participants, age 60-85, with a MOCA of 23 or higher. They will be recruited from the community. Participants will be randomized (approximately 30 per group). Participants in the 2 week arm will have 3 study visits: 1. Screening Visit: Consent and screening procedures will be complete. Participants will be randomized 1:1 to receive escitalopram or placebo. 2. Study Visit 1: This visit will take approximately 45 minutes - 1 hour; participants will have a lumbar puncture (LP) in order to obtain cerebrospinal fluid (CSF), a blood draw, and will receive study medication. 3. Study Visit 2: This visit will take approximately 45 minutes - 1 hour; participants will have a lumbar puncture (LP) in order to obtain cerebrospinal fluid (CSF), a blood draw, will receive taper-down study medication, and will complete an end-of-study questionnaire. Participants in the 8-week arm(s) will have 4 study visits: 1. Screening Visit: Consent and screening procedures will be complete. Participants will be randomized 1:1 to receive escitalopram or placebo. 2. Study Visit 1: This visit will take approximately 45 minutes - 1 hour; participants will have a lumbar puncture (LP) in order to obtain cerebrospinal fluid (CSF), a blood draw, and will receive 4 weeks of study medication. 3. Study Visit 2: Researchers will check in with participants and participants will receive another 4 weeks of study medication. 4. Study Visit 3:This visit will take approximately 45 minutes - 1 hour; participants will have a lumbar puncture (LP) in order to obtain cerebrospinal fluid (CSF), a blood draw, will receive taper-down study medication, and will complete an end-of-study questionnaire. The current proposal will test whether clinically relevant doses of an SSRI reduce CSF levels of Amyloid Beta in healthy older human participants. The investigators hypothesize that compared to placebo, participants receiving escitalopram will show significantly lower Amyloid Beta levels in the second CSF sample.