I don't know if I'd call it "placebo" for me; prozac gave me the worst, most horrible pit of sadness I've ever had in my entire life. I couldn't stop feeling guilty over every single bad thing I have ever done, and it completely killed my appetite and that probably didn't do great for my mood either. I was only on it for about two months until I begged my doc to get me off of it. She told me that it's one of those things that doesn't affect everyone, but since I was already taking Wellbutrin it can have negative effects.
Never again. I'm taking Pristiq now and that has been considerably better.