Teenagers who start smoking marijuana before the age of 16 are four times more likely to become schizophrenic. That's the startling conclusion of some of the world's top schizophrenia experts, whose research is featured in this documentary. Groundbreaking work on the connection between marijuana and mental illness also reveals that, for all young adults, smoking marijuana nearly doubles the risk of developing recurring psychosis, paranoia and hallucinations — the hallmarks of schizophrenia. The Downside of High tells the stories of three young people who believe — along with their doctors — that their mental illness was triggered by marijuana use. All three spent months in hospital psychiatric wards and still wage a battle with their illness. Today's super-potent pot may be a big part of the problem. Modern growing techniques have not only dramatically increased the amount of psychoactive THC in marijuana, they've also been breeding out a little-known ingredient called cannabidiol that seems to buffer the effects of THC. The Downside of High provides a scientific perspective on some of the little-known and little discussed risks of marijuana, particularly for teenagers.