I take anti-depressants but still get cycles of depression, sometimes it's a few days every two weeks or sometimes I can go a month or two of being alright.
Anti-depressants don't numb your emotions and you don't get high from them, they aren't addictive either except in the sense that they are a bugger to come off. I am not recommending you take them or anything, BTW.
If I only got it a few times a year then I probably wouldn't want to take them either.
I do think the winter has a big influence and if you are working nights you are missing the few hours of paltry sunlight that we do actually get, that must be rough. It might be worth getting SAD light.
Anyway, sorry for rambling, lol. I started off just wanting to add my support and say I know how it feels, so I will say that now.