This is not to downplay CTE at all but I was talking to a neurologist friend recently who believes that although CTE can trigger negative outcomes in people with already compromised autonomic and immune systems, it is likely not the sole cause of problems like you see here with Bannan. He believes even if you eradicated one contributor like CTE, you'd still have so much dysfunction in certain athletes especially if they were taking peptides, NSAIDs, cortisone (an immune suppressor) etc., over their careers, not to mention the heavy metals and pathogenic bacteria we have in our systems from our industrial and natural environment. This largely explains it in his opinion because CTE is likely more common than we know, and that many people live with it, somewhat impaired bu not pathological or even depressed. The problem is that we ingest so many things toxic to us and we live in toxic environments, so that the combination of all of this wreaks havoc on our systems (limbic, adrenal, autonomic, immune).