Actually, I'd like to make.a special mention specifically for tramadol, which I have found to be a pretty effective antidepressant, if taken at regular and reasonable doses (not as needed for stress - this will only build tolerance quickly and negate the long term effectiveness, at least in my anecdotal experiences with the drug).
As aformentioned, someone took tramadol at 150mg a day for a year without significant tolerance issues. This works if you are not looking for complete narcotizing doses to remain effective that long. For antidepressant effects, this does work effectively for much longer than you would expect from an opiate. The downsides include loss of the mild stimulation from norepinephrine effects after three or four months (replaced by typical opiate anhedonia - fix with caffeine and exercise), and of course the withdrawls can be tough if you don't taper.
Of course, if you need to stay on an addictive substance for a year to be happy, maybe the time would be better spent finding more permanent solutions for one's moods. I would only use tramadol for short term management of depression, maybe three months or so.