 Participation in this study will last 8 weeks, with follow-up assessments lasting for 6 months. Participants on a ventilation machine will be randomly assigned to receive either escitalopram, which is an FDA-approved antidepressant, or a placebo pill. A healthy surrogate may need to enroll participants in the study, because participants will begin treatment while in the ICU and may not be able to make an informed decision. The medication or placebo treatment will last for 2 months, continuing at the participants home after discharge from the ICU. Dosage levels will begin at 10 mg per day and will be increased to 20 mg per day for some participants after 3 to 5 weeks. Every 2 weeks, participants will complete questionnaires by phone or in person about their medical and psychological symptoms and about whether they are taking the study medication. At 8 weeks, participants will complete an in-person interview about depression symptoms, quality of life, and physical function. At 9 weeks, participants will complete a telephone interview about medication withdrawal. Finally, at 4 and 6 months, participants will complete interviews about depression and general health. 