I've been taking lexapro 10mg for six months or so for a social phobia and a general anxiety disorder. I didn't have any side effects when I started, but for the past 3 weeks, I've been feeling extremely tired. I've never been a fan of naps, no matter how tired I was I never could sleep during the day. However lately I'll alway fall asleep within 5 minutes if I close my eyes. Nothing changed in my life and my nights didn't get shorter. My question is, can side effects appear so long after starting a med or is this not related?