While many anti-drug advocates believed legalization would result in increased marijuana use among teenagers, the reverse seems to be true according to the latest numbers out of Colorado.

The researchers - as part of the larger Healthy Kids Colorado Survey - asked 17,000 high school students whether they had used marijuana during the preceding 30 days: 21.2 percent of Colorado high school students surveyed said yes: that's a slight decrease from 2011, when 22 percent reported they'd smoked pot in the previous month.

Although just under half of students polled - 48 percent - said they viewed regular marijuana use as a "risky" behaviour, some scientific research says they should consider it a threat to their health. "There are some reasons to think that adolescents may be uniquely susceptible to lasting damage from marijuana use," according to the American Psychological Association.

Until the early or mid-20s, "the brain is still under construction," according to neuroscientist Staci Gruber, PhD, and the frontal cortex - the region critical to planning, judgment, decision-making and personality - is one of the last areas to fully develop."

The number of kids trying marijuana hasn't risen since legalization, a central fear of anti-legalization advocates.

Parents influence choices their kids make

The study authors concluded that parents had the most influence over whether their children experimented with things like alcohol, tobacco or cannabis.

"If a parent feels it's wrong to use marijuana, their children are four times less likely to use marijuana," it said a press release about the survey. "If a parent feels it's wrong to smoke cigarettes, their children are six times less likely to smoke cigarettes. And if a parent feels it's wrong to drink alcohol regularly, their children are three times less likely to binge drink."

Dr. Larry Wolk, executive director and chief medical officer of the Colorado Department of Public Health and Environment, said young people generally follow the example set by the their parents.

"The Healthy Kids Colorado Survey shows parents who make healthy choices have children who make healthy choices," said Dr. Larry Wolk, executive director and chief medical officer of the Colorado Department of Public Health and Environment. "This comprehensive survey of youth behavior lays out the path to a healthier generation of Coloradans."