Part of it has to go be the people pushing kids to the NBA and the system that helps funnel them there.
I think of this video of future NBA players watching Blake Griffin dunk in the summer of 2012. A lot of these guys are 15 (Booker, Stone) and 16 (Vonleh, Russell, Lyles, Briscoe, etc.) years old, and the system has already figured out who the future NBA prospects are and gathered them all together. This isn't just random chance here that these kids all ended up at this event, these are kids who for years have likely spent all year grinding, working out, and on the AAU and Sneaker Camp circuit to get noticed. We're talking 6am workouts, school, practice, more workouts/homework, wake up and do it all again the next day. If a kid even has the slightest bit of potential to get that money, fame, power of being a pro athlete, people will recognize it early and push that kid there, ruining a lot of childhoods in the process. This comes from both well meaning parents/coaches as well as the leeches and hangers on who want to get a piece of somebody else's hard work.
We all know the story of how messed up Michael Jackson was, thanks to Joe Jackson pushing him (whether or not you believe the allegations, you know MJ was messed up). It's like that a lot of times, but with basketball instead of music.
And it doesn't stop once you get selected to the McDonald's game, or get the scholarship to an NBA factory like Duke or Kentucky, or become a lotto pick, or make the NBA. Every step along the path just adds more pressure. Now if you don't make it you're a joke (Anthony Bennett, Darko, Morrison), if you do make it, you deal with fans wanting to trade you, analysts saying you're not good enough, and wondering if anybody really likes you for you. Is every girl you meet just a gold digger? And can you really trust any friend you've made since you were tagged a basketball prodigy at age 12? Everyone just wants your money or to be friends with the basketball star, right?
You didn't have a normal childhood, constantly pushed to the limit since your early teens, with constant pressure and media scrutiny. I can see how this could cause people to crack.
I think it's very, very similar to what goes on in the Ivy League. Obviously different world but similar situation. You've been given this great opportunity to make something of yourself, everybody will be disappointed if you don't, and there's huge competition with everybody gunning for your spot or to get that internship or job offer or whatever. You spent your junior high and high school years studying, taking AP and college level classes. Spent your weekends doing SAT prep courses, or volunteer work, or something else to help make you stand out to admissions. Not a normal childhood, constantly pushed to the limit, with constant pressure to succeed.
It's why Ivy Leagues have high suicide rates and terrible mental health grades. Or you can read Jeremy Lin's piece on the "Silicon Valley suicdes" and the pressure those high school kids feel. I'm sure it's similar to how a lot of athletes feel, just swap out gpa with ppg.