Colorado kids aren't smoking more pot since the drug became legal - but their older siblings and parents certainly are.
Those are the findings of a long-awaited report giving the most comprehensive data yet on the effects of the US state's 2012 recreational marijuana law.
Surveys of middle-schoolers and high-schoolers indicate that youth marijuana use hasn't risen much since the 2012 vote.
Anonymous surveys given to about 40,000 students before and after legalisation show "no significant change" in marijuana use by children under 18 in the preceding 30 days.
Among high school students, use went from about 23 per cent in 2005 to about 20 per cent in 2014, while use by kids under 13 was similarly little changed.
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Youth marijuana arrests in Colorado rose five per cent between 2012 and 2014, from 3,235 to 3,400, but pot arrests in schools soared by 34 per cent.
Looking to adult data from the national drug use survey, Colorado reports nearly a third of adults 18 to 25 in 2014 had used pot in the last 30 days, up about five per cent from the year before recreational pot was legalised.
There was a similar spike in adults over 26, with past 30-day marijuana use rising from 7.6 per cent in 2012 to 12.4 per cent in 2014.
The numbers also show a marked drop in arrests overall - a major argument of pro-legalisation activists - but more traffic fatalities in which a driver tested positive for marijuana's psychoactive chemical THC.
