Marijuana use rises in states with legalization

1. Past-month marijuana use in Colorado and Washington state rose following the legalization of personal possession, according to new data from a federal survey.
2. Nationwide, Americans reported smaller percentage point increases in marijuana use than people in Colorado or Washington.
3. But the data doesn't include marijuana use rates for 2014, the first year of legalized sales.

A federal survey found big increases in Colorado and Washington state

A customer inspects marijuana in one of Washington state's first recreational stores. (David Ryder / Getty Images News)

The National Survey on Drug Use and Health (NSDUH) broke down state-by-state marijuana use during a 2011-2012 period and a 2012-2013 period.

The survey found reported past-month marijuana use among Coloradans 12 and older increased from 10.4 percent during 2011-2012 to 12.7 percent during 2012-2013. In Washington state, use among the same age group increased from 10.2 percent to 12.3 percent. Nationwide, use nudged up from 7.1 percent to 7.4 percent — a much smaller increase than either state.

The increase appeared to occur almost entirely among adults. Among adolescents aged 12 to 17, past-month marijuana use went from 10.5 percent to 11.2 percent in Colorado and 9.5 percent to 9.8 percent in Washington state — neither of which are statistically significant increases. But among adults 18 and older, use increased from 10.4 percent to 12.9 percent in Colorado and 10.3 percent to 12.5 percent in Washington state — both statistically significant.

Other surveys released in the past year found marijuana use didn't increase among teens in Colorado in 2013 and nationwide in 2014.

Colorado and Washington state in late 2012 became the first states to legalize the possession of marijuana through voter-approved initiatives. But neither state began selling pot in recreational outlets until this year.

The results don't say anything about recreational marijuana sales

A marijuana dispensary prepares for the launch of recreational sales in Colorado. (RJ Sangosti / Denver Post via Getty Images)

The big question for marijuana legalization in Colorado and Washington state is whether recreational sales will lead to more use. But sales began in 2014, a year after the latest NSDUH data.

The survey data could indicate that the medical marijuana industries in Colorado and Washington state are driving up use.

"This is not surprising given what's going on on the medical side," Mark Kleiman, a drug policy expert at UCLA, told the Denver Post. "I don't think this tells us about the long-term impacts of legalization."

A comprehensive study of medical marijuana laws from researchers at the RAND Corporation found policies that allow medical marijuana dispensaries correlate with increases in overall marijuana use and dependence for adults 21 and older but only rises in dependence among youth. The findings suggest that the commercialization of marijuana may lead to more access and use, particularly among adults.

But these numbers could miss underlying trends. Another study from RAND Corporation and Carnegie Mellon University researchers found that focusing on number of days of use instead of overall use rates shows much larger increases in marijuana use, suggesting that people who already use pot have been consuming more of it in recent years. But, as with the NSDUH data, most of the increase occurred among adults, not youth.

Read more: 3 things we learned from Colorado's first year of legal marijuana sales.

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