There needs to be far more investigation into CTE. There have been studies etc in America and there was at one point a class action lawsuit against the NFL from players because of the long term effects of CTE.
Apparently American Footballers have got higher risk of developing CTE because despite the helmet, recurring concussions still happen. From memory it’s to do with the brain being damaged when players are being tackled, which a helmet can’t prevent.
Any contact sport which leaves the player open to recurring blows to the head or concussions need to research this, because there may be a correlation (there has been no official cause and effect proved) between CTE and increased aggression/reduced brain function. When coupled with drug/steroid abuse this issue creates huge volatility and is a disaster waiting to happen.
There have been some tragic cases which CTE have played a part in with one in particular of a wrestler who killed his wife and child before killing himself. When his brain was examined post-mortem, the CTE organisation said that due to recurring concussions he had (in his mid forties) the brain of an 80 yo dementia patient.