Unfortunately people die in HS. So sure, if someone played HS ball, then stopped playing, lived until 60, and got CTE, it would be hard to say it was from HS ball, however when someone dies at 18, and is positive for CTE, that's pretty definitive.

I read somewhere that even one concussion can triple the likelihood of someone suffering from depression later in life. That's pretty scary stuff. Our heads are not meant to be banged against things, so I would think that goes double for a developing brain.

Right but your sample size is pretty big. Like I’m pretty sure the other factors can be controlled for. Dont take my word for it, these are the general conclusions.