I'm not a teen, but as an adult, I started on lexapro (well the generic version of it) due to anxiety and grief recovery a year ago. It has really helped me out. The first couple of weeks I felt a bit worse before I felt better. I did have some uncontrollable leg shaking (like a nervous tic) as I ramped up to the full dose. I think for the first week you take 1/2 a pill. It has really helped my anxiety a lot. Yeah, there was a bit of weight gain, but it was worth it for me. I do feel my emotions are a bit "deadened", but I still feel things. It's hard to explain. Rather than emotions going up and down, it's more of an even keel. I will be on it for a while. Yes, Dr's don't say to start and stop this medication willy nilly. I would say it took a good 2-3 months before the medication really kicked in. I was really really freaked out by SSRI's and reading the warning labels and side effects, but it was worth it.