I put no, but I'm not quite sure what you mean by shifts.

When I was on Lexapro the problem was I had to take it during the day (fairly unusual) because it kept me awake, but it would give me a high for about 3 1/2 hours and then it would drop me back to a pit of despair lower than the one of that morning.

Obviously it wasn't working for me but that was just my experience on it