Everyone seems hung up on causation. I'm just talking about how something that glues your ass to a couch isn't necessarily the best thing to combine with a disease that also saps volition.

Sure, you don't feel it so strongly while you're high. That's one of the nicer things about that particular drug, paranoia aside. But that only works while you're high, subject to the same habituation process as anything else - and it's not the same as actually doing something to help yourself.

I don't doubt there are people with depression for whom marijuana has been a substantial help. That's great! I'm glad for them, and that legalization is making it easier for people whom marijuana helps to maintain access to it. I also think it's reasonable to approach marijuana with the same caution as any other potentially beneficial drug. Arguing that, because there's no uncontested evidence that marijuana causes depression, there's no harm it can possibly do a person with depression - does not seem all that cautious to me.