"The other question is, are youth getting the message about the fact that using marijuana during adolescence is more harmful because of their brain development?" Halpern-Felsher said. "Given the legalization, we need more education around marijuana or cannabis use for youth and we don't really have a lot of education."

Quite. There is a need for more education, especially for the idiots in the state legislatures that are writing the legalization laws. Although I suspect there will be an ever increasing mountain of evidence to back up that already compelling evidence that the "legal age" should be at least 25. Of course, state legislators cannot be arsed into following science when there's the supposed appeal of big tax revenue. Never mind that pot does NOT generate anywhere near what was promised.