Hi Christina,
There are others that can give a better answer on this than I can, I'm sure.
However, I just thought I'd tell you what I've heard from my dr. If you take Xanax (anti anxiety meds) they can work very quickly but antidepressants (lexapro, paxil, zoloft, etc.) take time to get into your system. Some can take up to four weeks!! When I had stopped taking Zoloft & had to go back on my dr told me 1-2 weeks (I had only stopped taking them for several days) within a week I felt better, 2 weeks I was pretty good, but it was about 4 weeks before I felt 100% again. According to my dr they are very slow acting drugs. He also says that is one reason they are not addictive, because you get no immediate feelings from them like you would with Xanax or other antianxiety meds.
Chanda