Well, yeah. The ability of humans to self-delude themselves is well-known, and of course mental illness exists as well.
It seems a little silly to say "I believe these experiences exist"; it almost sounds like you're trying to imply that some greater force exists. It's reminiscent of those people that say "well, I don't believe in God, but there has to be something" as if they'd just uttered a profound statement.
It'd be silly to doubt that at least a small portion of the people reporting experiences believe they experienced whatever they said.
It seems a little silly to say "I believe these experiences exist"; it almost sounds like you're trying to imply that some greater force exists.
Beliefs have to pay rent.
Would you start believing in some greater force if someone demostrates to you that those experiences exist by guiding you through the experience?
How much different kind of spiritual experiences would you need to experience to drop your belief in materialism?
The Wave: In Pursuit of the Rogues, Freaks, and Giants of the Ocean is a book about very big ocean waves-- the science, the danger (mostly to ships), and the surfers.
Really big waves weren't scientifically verified until about ten years ago-- part of the problem was that even though sailors had been reporting huge waves, scientists had a theory that big waves (maybe over 80', though I don't have a sharp dividing line) required very rare conditions. Once satellite surveillance for waves was possible, it turned out that big waves were fairly common, and might explain why a ship or two per week disappears.
Russell Wynn: "The way the radar system works, the very big ones are difficult to measure," he said. When behemoth waves appeared in the satellite data, the space agencies considered these readings to be errors, and they were automatically deleted. "They give you missing value code instead, which is really annoying. We shout at them for that."
The reason I'm posting this is that I've become very skeptical about any theory which claims that something which is well-attested and physically possible is actually not happening.