https://www.latimes.com/local/la-xpm...html?_amp=true
https://azdailysun.com/passenger-pil...49b480d75.html
https://www.sandiegouniontribune.com...html?_amp=true
Obviously rare but it does happen.
Can’t find the news link but I believe it was Florida where a person jumped during an introduction flight for the instructor to return alone.
Personally I wouldn’t fly with a person with any mental retardation.
Done that once and it turned into an immediate turn for downwind and expedited landing.