He was doing the "My good friend" act because he wanted to show famous people who also had it, his whole idea was to take away the stigma of mental illness and show role-model type people who were willing to talk about it.
Wasn't Kerry Fisher really scarey? She looked awful (so does her ex, Paul Simon, mind). I know someone like that in real life (also diagnosed bipolar) and I find her equally sad/scarey. I know a lot of bipolar people, though, so think I'm over-sensitised.
Depression does run in families, really strong in mine .