Has it been proven they have nothing to do with it, or that it isn't the primary cause?
Well the research used to suggest it was caused by repeated small microtraumas like linemen experience basically every down, rather than by concussions. The upshot was that the league was ignoring this by focusing on concussions in order to say they were dealing with the problem.
Now apparently the research says it's both - concussions and repeated smaller impacts.with no concussion symptoms.
So I was incorrect when I said concussions have nothing to do with CTE. The experts still believe football players are at risk of CTE whether or not they have a history of concussions.
www.bu.edu
"We believe CTE is caused by repetitive brain trauma. This trauma includes both concussions that cause symptoms and subconcussive hits to the head that cause no symptoms. At this time the number or type of hits to the head needed to trigger degenerative changes of the brain is unknown. In addition, it is likely that other factors, such as genetics, may play a role in the development of CTE, as not everyone with a history of repeated brain trauma develops this disease. However, these other factors are not yet"