They prescribed Lexapro for my step-father when he was in the hospital. He was having terrible mood swings and would lash out at the hospital staff also. After about three days on it, his eyes sparkled and he was tooo happy. Mellowed out since then. I always thought it took a couple of weeks for certain meds to start working, but it was a couple of days in his case. I am glad he is on this, as it helps with the depression of finding out he has cancer. I think it is like Paxil.