How long can it take for lexapro (escitalopram) withdrawal to set in?

Varies, couple days: Withdrawal from an antidepressant is a subjective experience that does not track with drug levels - and does not even happen to everyone to stops antidepressants. While withdrawal is theoretically possible late in the day of your first dose (assuming you take it in the morning), it becomes more likely the second day, and increasingly likely each day after. (In seniors, it may take longer.)