There was a better article in a medical journal that came out this week. The doctors say they haven't narrowed down correlation V causation yet. Just that almost all players that they've tested have CTE. Not just pro, but highschool and college as well. High school players have a lower percent than do the college players than do the pro players.

They go on to say that people donating their brains to the study are also people who are experiencing issues and are looking for answers. Some football players experience no symptoms throughout their lives. That's not to say that football isn't the cause of the CTE in the examined brain, just that there's not enough info to make an informed diagnosis. They know it's not final data just yet but as PB said, the current working theory is the sub concussive hits.

I suppose it's like people who smoke cigarettes until they are 100 and never get lung cancer. Doesn't mean that cigarettes don't cause cancer, just that it doesn't always cause cancer.