Nick has talked about his struggles, including with substance abuse and self-harm. I think it's cavalier of you to keep playing his doctor and therapist here. You don't know that his issue is being bipolar. You certainly are in no position to diagnose him or to prescribe medication for him. It's a serious thing, and I don't think you should take it lightly, or fling the term "bipolar" around like it is a blanket synonym for mental health issues. Whether you intend it or not, it sounds like you're making fun of it.
@Kieran: It may be that he's not innocent of the charge, and his state of mental health is his only defense. I guess we'll see how this plays out, because a certain amount of it will be public.