From a Scientific American article:
"A 2013 meta-analysis, combining much of the existing data, by Jim van Os of Maastricht University in the Netherlands and Richard Linscott of the University of Otago in New Zealand, found the prevalence of hallucinations and delusions in the general population was 7.2 percent."The main thrust of the article is that schizophrenia may exist on a spectrum like autism does. However I find the idea that hallucinations might not be uncommon pretty damning to ufology. Especially the Streiber style experiencers.
What are the implications for UFO research? If this is true then it would discredit experiences where there is a single witness with no corroborating evidence.