The interiors could be staged but I doubt it. The series is meant to spur dialog on what if anything should be, could be, done to help people who seem to be falling between the cracks. Especially veterans.
While you don't see handguns on car seats in Canada, you certainly do see the rest. Especially in WalMart parking lots. I'm certainly not is a position to make broad sweeping generalizations but in my personal experience with messy car interiors (basically a traveling dump) the person who owned the vehicle had some form of mental instability. Some higher functioning than others, but certainly in need of help.
Eric