Did Glen Campbell's struggle with alcohol and drug abuse cause his Alzheimer’s disease?

According to Glen Campbell's doctor Ronald Petersen in an interview with Today.com, saying alcohol or drug abuse caused Alzheimer’s disease is probably stretching it, "because it would mean that alcohol or drug usage actually leads to the development of plaques and tangles in the brain, and we clearly don’t know that".  On the other hand, Petersen said, "severe alcohol use and certain drug behaviors can compromise the brain’s resilience. If we’ve had certain insults over our life — be it alcohol, drugs or head injuries — that may reduce the ability of the brain to compensate for the development of either aging or Alzheimer’s-type pathology. Other people who have not had those kinds insults might be able to compensate — their brains might be more plastic, more resilient — and stay functional at a higher level for a longer period."

Link to original story on Today.com