Repeated blows to the head can cause addiction problems, and depression...
So your biggest factor is caused by blows to the head, which does need to be studied more, but they're finding out a lot quicker than they expected, especially with all the brains they're being donated that have cte.
So its all the same homes.
The opioid painkillers themselves can cause depression and a complete change of character. I know I felt like crap on them after my surgeries, I would rather feel the pain. These guys are prone to broken bones because that's what they get paid for, I guess the million dollar question would be is it head trauma that's responsible for the downfall of the enforcer types or the lack of need for those types of players in the evolving NHL that lead to the spiraling out. When you go from making six figures to working normal everyday jobs that has to play a part in depression as well.
It's a sad situation nonetheless and I hope the studies pan out.