Its different for everyone it seems
I was on Prozac (20mg) for about 7 weeks, was sh*t for me.
The only effect was insommnia and terrible nightmares.
I'm on Mirtazapine now, which is pretty good. I think.
My nurse in hospital told me that anti-depressants don't actually make you any less depressed

weirdly enough,
Apparantly the effect they are supposed to have is to (in his words)
Make you care less<--- I'm not sure what that means
Maybe it lessens the more physical stressful symptoms of depression.
I know I can sleep more and better and I'm a bit less anxious on this one.
Meh, rambling now, who knows!