Bipolarity, I believe, is the term.
Whoo, that song rocks.
My dad is bipolar, and both my brother and sister have depression and take medication for it. I don't know about my sister, since she's been taking it for quite a while and my memory doesn't extend back that far, but I know it really helped my brother. Both sides of my family have a lot of mental illness. On my dad's side it's depression and bipolarity, on my mom's side there's paranoid schizophrenia, autism, all kinds of stuff... No wonder my parents are both psychologists.
