Is there a rule somewhere...

that says when writing a New Adult novel all characters must be broken people? When reading the synopses of books in the genre, I find that many, if not most, of the MCs are depressing, broken people who get involved with people who are even more depressing and broken than they are. Are New Adults broken and depressing people? And furthermore what is the age range of New Adults?

I have not yet tackled this genre, but have enjoyed the reviews of others who have traveled this brave new world. So I ask you brave few....