According to a research review by the White House Office of National Drug Control Policy. Federal drug czar John Walters said that while the rate of mental illness is about 8-9% among U.S. adults, the rate is 12.5%  among those who use marijuana. Among those who used pot before age 12, mental-illness prevalence jumps to 21%, said Walters.

“We’re trying to get out the word that the last 10 years of research have helped to alert us to the use of marijuana in particular is a very dangerous risk for the mental health of our young people,” he said. The data cited came from the National Survey on Drug Use and Health, a study of twins published in the Archives of General Psychiatry, and other sources.