My experience of the whole subject is similar to that of SteveP. I don't have a chemical imbalance causing 'depression' but just seem to be on a constant downer. As in Steve's case I lost my job a while back, all of my mates have moved away and despite being a fairly affable kind of guy, it's hard to make new friends without old ones to go out on the town with. In fact, apart from parental clips 'round the lughole, pretty much everything SteveP said rang true (and add to that daily schoolyard-kickings as a kid).
It's funny, when I look at it written down my first thought is "Shut up whingeing, you cunt, some people have got real problems", but the only difference that makes is to make me feel even more of a cunt. Maybe I am. Maybe I'm depressed. It's hard to tell when the only people you speak to regularly are your parents, who think that if you get a job everything will be fine again, and the dole, who think much the same.
I read James' account of attitudes among his mates regarding anti-depressants with great interest. Although their comments no doubt were informed by ignorance and fear, when I was prescribed Prozac it did have the unpleasant side-effect of a kind of manic, edgy feeling of happiness, like believing I had superhuman drinking powers where I could destroy entire bottles of scotch in world record time and think I was having a great time but was in fact I was just trying to silence my brain's incessant thinking. Kinda like "God, I'm so happy I could smash my head... [thunk!] against... [thunk!!]...a fucking wall...[thunkthunkthunk!!!].
At that time my odd behaviour caused me to fall out with a close friend. Years later I was sat with him in the pub and he suddenly turned to me and said he was sorry he had been such a shit that weekend because he had himself taken Prozac more recently and it had exactly the same effect on him. I actually found out later from a family friend who suffers depression in the chemical sense, that this is common in users and goes away after a couple of months and that the same drugs that made me go off the rails had saved her life on many occasions.
I guess the moral of the story is eveyone has a slightly different experience of it all and what works for some can be bad for others.
The human brain is an infinitely complex machine and some fucker forgot to include the instruction manual...