Cannabis is probably a bad idea if you suffer from depression. Supposedly, Chronic use will cause your dopamine receptors to (temporarily) atrophy, causing you to get less pleasure from "life". This is the reason that not smoking weed when you've been chronic for a while sucks and makes you irritable.

I would recommend picking up an active hobby like hiking or juggling or something like that.. Maybe get religion. I don't know, I've never had a problem with depression, I guess it probably shows.

You might try Kanna, it's a natural SSRI.. Quite potent, though, so careful.