My peers who went onto get PhDs without going to industry were... different. Not necessarily super smart, but not the best socially or in leadership positions.

I can think of 3 people that were getting their PhDs in engineering, but I thought they were average students at best. One was an average to below average working with me on labs. Another was just a goofy weirdo, I couldnt be friends with him because he'd shoo me away. Another was somewhat a brainiac, but to a fault, He'd get As, but didnt really have friends from what I could tell.

I imagine lots of this is correlation not causation, and that things are different at big names schools.

That can very well mean 1/3 of Americans get depression over their entire lives, and a PhD program would seem like the time to get it.