Damage to my inner ear as a result of barotrauma on a long-distance airplane flight, sparked by eustachian tube dysfunction, caused my tinnitus, I believe. (although not every doctor I have seen agrees. But most do).
However, I had gone through three years of incredible stress prior to this incident, due to rolling lay-offs and increased demands at work. I believe while barotrauma pulled the trigger on my tinnitus, extreme stress loaded the gun.