DENVER – Teen marijuana use has declined since retail legalization was backed by voters in 2012, according to statistics released Thursday by state health officials.

Thirty-day marijuana use fell from 22 percent in 2011 to 20 percent in 2013, and lifetime use declined from 39 percent to 37 percent during the same two years, according to the Healthy Kids Colorado Survey released by the Department of Public Health and Environment.

“Regulating marijuana is working in Colorado. The drop in teen use reflects the fact that state and local authorities have far more control over marijuana than ever before,” said Mason Tvert, a proponent of Amendment 64, which legalized recreational marijuana, and spokesman for the Marijuana Policy Project. “Hopefully, elected officials and voters in other states are paying attention.”

Teen use in Colorado dropped nearly 5 points since 2009, when hundreds of medical marijuana stores began opening throughout Colorado. The state began regulating medical marijuana in 2010.

Durango is set to implement retail marijuana this fall.

Dr. Christian Thurstone, a specialist in child and adolescent and addictions psychiatry, will speak Friday at the Community Cannabis Forum in Durango at Miller Middle School. Thurstone is expected to present on the impacts of marijuana on the adolescent brain and discuss the implications of Colorado laws.

The trend in Colorado appears to debunk theories that marijuana legalization and normalization would lead to a spike in teen use, though retail marijuana opened for business in Colorado only in January.

Nationwide, the rate of current teen marijuana use increased from 20.8 percent in 2009 to 23.1 percent in 2011 and 23.4 percent in 2013, according to a report released in June by the U.S. Centers for Disease Control and Prevention. The national rate of lifetime use increased from 36.8 percent in 2009 to 39.9 percent in 2011 and 40.7 percent in 2013.

But in Colorado, where marijuana has seen a popularization and commercialization, teens appear to be moving away from the drug.

“As the culture normalizes cannabis into it, what’s happening is that adults are setting a good example of cannabis use, and kids are finding it kind of boring,” said Shawn Coleman, a Colorado marijuana lobbyist.

But state officials point out that the percentage of students who perceive a moderate or great risk from marijuana use declined from 58 percent in 2011 to 54 percent in 2013. They continue to worry that normalization of marijuana use in Colorado could lead to more young people trying it.

Officials also point out that none of the usage declines represents a “statistically significant” drop since the data is based on a sample with a margin of error.

“If we want Colorado to be the healthiest state in the nation, then we need to make sure our youngest citizens understand the risks of using potentially harmful substances,” said Dr. Larry Wolk, executive director and chief medical officer for the state health department. “Later this month, we’ll launch a youth-prevention campaign that encourages kids not to risk damaging their growing brains by experimenting with marijuana.”

Gov. John Hickenlooper, a Democrat, has been very concerned with the marijuana legalization experiment in Colorado, especially the impact on young minds. A grant in partnership with the city of Denver and the attorney general’s office has funded a campaign in which the symbolism of a rat cage is employed with the message: “Don’t be a lab rat.”

The state also has allocated $16.4 million in marijuana tax cash fund expenditures for education.

“We know what works to protect young people from unhealthy substances,” Wolk said. “As with tobacco, youth education prevention campaigns will help ensure adult legalization of marijuana in Colorado does not impact the health of Colorado kids.”

He said that Colorado must continue to address the potential risks of using marijuana.

“We need to make sure our youngest citizens understand the risks of using potentially harmful substances ... “ Wolk said. “The fewer youth smoking marijuana ... the better.”

pmarcus@durangoherald.com