Yes, I definitely believe. Most of my hubs allude to the workings of the soul.
Regarding your second question, “what accounts for significant changes …”, my answer is that the soul’s purpose always overrides the physical or bodily requirements. Our conscious or cognitive reasoning, on the physical level that may dictate for us to be acceptable to the society cannot override the soul’s agenda, which is beyond our conscious intellect to grapple with. So, if in the higher order of things, to which the soul’s agenda aligns with, it is called for that an individual’s cognitive (conscious) function should be altered, it will be altered.
(In the Christian perspective, I would speculate that an altered state could be a visit from the Holy Spirit, overriding the conscious faculties of the individual, to serve greater purposes in the Master Plan.)
In short, the body’s demands cannot overrule the soul’s purposes.
The reasons are usually beyond immediate human comprehension, but eventually are revealed in time.