Oh, I must have missed that one. My apologies.

I think that it can be both or one or the other.

I've had many traumatic events in this life and my personality itself has been altered before as an effect (voice, accent, behavior...etc) or defense against the trauma itself.

In my experience, I blame reliving past lives in quick succession at the point of death for the changes experienced afterward.

Otherwise it could be explained through brain damage, which is not detectable in any scans I have had.

In my opinion, a soul exchange is very different in comparison to a soul alteration formed at the point of near-death. A true Soul exchange is far more significant.

This is only my opinion though, others would say differently.