A new RTI International research study shows that the frequency of marijuana use within the last month is an accurate indicator in predicting the likelihood and rate that medical marijuana laws will be passed and implemented in a state.

“Marijuana definitely has some contraindications with pain medications, so it’s important for clinicians to understand that their patients may be using marijuana as a supplement,” said Scott Novak, PhD, study author and senior developmental epidemiologist at RTI International.

The research was presented at the PAINweek conference this week in Las Vegas. A full summary of the study and a video can be found at Pain Medicine News online, who first reported the findings of Dr. Novak and the research team from RTI.

“We found that over the last decade or so, past-month marijuana use had been increasing and there had been a corresponding decrease in risk perceptions over time,” said Novak.

The researchers found that overall marijuana use increased from 6.5% between 2002 and 2003 to 7.3% between 2011 and 2012. States with medical marijuana laws consistently had higher marijuana use, from 7.9% in 2002 to 2003 to 9.6% in 2011 to 2012, than states without medical marijuana laws , which averaged 6% to 6.2%. States with medical marijuana laws also had a greater decline in risk perception, a trend that started around 2007.

“People have been very curious to understand really what happens in terms of the chicken and the egg, whether marijuana use is increasing after legalization. What we’ve found is quite the opposite,” said Novak.

Medical marijuana is currently legal in 23 states and the District of Columbia. Marijuana has been legalized (the term “decriminalized” has also been used) for recreational use in four states and the District Columbia.

In a recent announcement from the Bernie Sanders campaign, Sanders announced his intention to legalize marijuana as a federal policy, and he later introduced legislation in the U.S. Senate that would do so.