Wow, and yet, my totally unprofessional opinion of dehydration is -still- probably the most accurate.
It's extremely common that younger riders don't think to hydrate.
its also nanny-state where everyone assumes the worst right off the bat. Diabetes, hypoglycemia, damaged internal bone structure.. geez guys. Don't forget the basics.
(On that note I am pleased to see there are resources here for more in-depth issues. cheers on that.)
my diabetes thing was for the kid above me that gets bad vision but food makes it better better safe than sorry