We don't have numbers and sources about people who are high because the government considers the drugs illegal, and it puts no funding into research on the drugs, or finding numbers of the drugs. I may be wrong, I just got the idea from the great depression example history gave me.
If there are no facts, then you shouldn't have an opinion. But there have been studies, of course, and of those 10,000+ studies, 12 have found negative effects caused by marijuana use. In the '70s, there were three large field studies of marijuana conducted in Greece, Costa Rica and Jamaica. These three studies concluded that marijuana was a relatively safe drug.