I don't want to help my friend overcome depression
Why would you not want to help them?
I think he makes a bad company because of his mood swings. I can't help him that way.
You should always be there for your friend. They are depressed and need your help. Try to help him.
Nah, I have enough mood swings to deal with.
Even if you personally can't handle the mood swings, maybe you can help him find someone that can.