I don't think it would be a problem if the person you want to be involved with or are involved with takes care of themselves (with therapy, pills, whatever works for them, etc).
I'm currently involved with T, and he has Tourette's and another mental issue but has taken control of his disabilities and he controls them, not the other way around. I admire him for that.
On the other hand, unless you feel the need to help someone with issues and you have the willingness to be hurt if things don't turn out, than all power to you.
Don't know if this adds anything to the conversation, but it's my two cents. =)
B: (me) female, poly, straight
M: (my husband - married 5, together 13) male, heteroflexible
A: (our, myself and M's 2 year old daughter)
C: (my LD boyfriend) male, mono, straight