Luke: For me it is my father. He is diagnosed as bipolar, but the functional part (which is so much more pragmatic, in a way) of the problem is that he has no skills at interacting with people. He has no interior emotional world that he can understand others through. He's a huge brain that doesn't understand what motivates 99% of the people in his life - and therefore doesn't have too good a handle on what motivates him.
He rails against the WTS doctrines in the same breath he begs to be made one with them.
Depression is an illness, and meds can give a buffer - but the two things that will help depression are the desire of that person to change their baseline experience, and therapy. Meds alone can make things seem better, and can open some space for reflection and motivation towards action, so they can be a good step in the right direction.
But I'm sure you know all this already, this isn't news...I hear you...we still love them, though they seem so different in their capability to cope...