Leaders in the health sector from Washington state and Colorado, where marijuana's recreational use is widespread and often ineffectively regulated, know enough by now to take a step back and consider the ill effects. They presented findings and concerns on the health effects of cannabis Thursday afternoon at a National Academy of Sciences committee meeting in Washington, D.C.

Dr. Leslie Walker, chief of adolescent medicine at Seattle Children's Hospital, added her pediatric view to a Colorado public health official's report of pot users coming to the ER with grave physical symptoms. "For kids, it's actually not uncommon. We have a number of them in the hospital at the same time. It's not just the long-term users," she said.

The disruption of a growing brain's normal development is a heavy concern. Walker observed that research of particularly tragic cases has established links between schizophrenia and adolescent marijuana use. "People who use fifty times or more were much more likely to have a diagnosis of schizophrenia than people who had never used," she said. And a more pervasive, less dramatic side-effect is permanent cognitive impairment. One widely covered study found regular marijuana use accounts for a loss of five to seven IQ points—but counting the often overlooked fact that the average non-user gains three IQ points during adolescence, the teenage pot user's developmental loss is even greater. Marijuana stunts mental development, and often irrecoverably.

"The other part which is concerning," Walker added, "is there are poorer treatment outcomes when you compare them to adult users."

New methods, like dabbing and binging on cannabis-infused candies, increasingly land Seattleites in the ER. Walkers said 11- to 19-year-olds and 20- to 29-year-olds account for most of the calls and visits—and increasingly so 2013.

The Department of Transportation, on the other hand, contributed results of a roadside study to show that driving while high causes fewer auto accidents than drunk driving. These findings support the standard stereotype that stoners are more risk-averse than drunks. In downplaying the dangers of the drug, the message of the driving study diverged from the medical perspective.