Hallucinations can be caused by all sorts of reasons, even in an otherwise healthy person. When I was recovering from PTS I used to have a lot of hypnogagic hallucinations. Fortunately I knew what they were from classes I took in psychology. Otherwise they might have sent me running back to religion. It makes me even more grateful for my education.

I think most of the time they are just mistaken. Not a ghost, but when I was a young man out driving in my first car, I thought I saw a UFO. It was a slightly misty night, and down in the valley below the road I was driving on, I saw a round glowing ball of light traveling at speed and jumping over the field boundaries. The effect was totally convincing.

The following night I saw it again, but that time I stopped and got out of the car. Then I heard another cars engine, and then I realized that there was another road parallel to mine down in the bottom of the valley, which I had not even been aware of, and all I was seeing was a strange effect that car lights were making on the mist. Had I not bothered to stop, I would probably still to this day be convinced .

By the "law of averages" people have overlapping but not identical aptitudes so some of them are probably balanced enough to be reliable (even when in "distress" incidentally). In some cases there have been a range of Unrelated witnesses. As to "what" - events might get imprinted on some fabric of the universe but as we neither know how, nor are really impacted (mostly) I think it is very close to being a non-question.

Videos and photos incidentally aren't a strongly convincing means of evidence unless you had rare inside means of knowing it unusually sound. Occasionally someone has been seriously bothered and occasionally someone managed to "do something about it" and sometimes this hasn't worked and sometimes people "live with it". Specific manifestations have their locations and are usually attested by unrelated people.

It is also natural for central nervous systems to attribute symbols to sensations (which are of far more than 5 kinds) (individually) and this isn't "confabulation" either. The cooler we all get about accepting varying "experience" as just that, the better for everybody. As to ghosts (and I haven't seen or felt one myself) they are in my opinion unsensational, overall.

They could also be not schizophrenic or liars and their mind could be fooling them. The more we learn the more we know our vision and perception are far from exact reality.

All three are possibilities. Some people might be mentally ill, and more than a few people are liars, and in some cases it could be due to the effect of drugs (either legal or illegal). But no one has ever proven that ghosts are real despite countless attempts, a multitude of investigative reality TV shows, and advances in technology.

No, I have experienced a ghost and that is that. No extra dimensions, no energy spike, no mental problems.