Have you ever been abducted by a space alien?
Reporting in the prestigious Psychological Science (as seen in this month's Scientific American) reports that it doesn't matter whether the victim was really and truly abducted by a space alien (and who knows what sort of Walmart-induced otherworldly liberties were taken), the psychological effects are identical. Patients hearing a script recounting their alleged horrors experienced identical response to soldiers and others suffering post-traumatic stress syndrome.
In other words, if someone believes something is real, then the effect on them is the same as if it were real.
Psychophysiological Responding During Script-Driven Imagery in People Reporting Abduction by Space Aliens
Leaving ET aside for a second, this is a profound (if obvious) result. What we experience is far more driven by what we believe than by what the objective truth may report. Stories come first. Authentic stories hold up under scrutiny. Manufactured stories dry up and fade away. But stories come first.