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Teens didn't start smoking more weed after medical pot was legalized

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Another study shows medical cannabis doesn't matter much for teen drug use

The debate on legalizing medical marijuana is still raging across the US, even though 23 states and the District of Columbia, have now legalized pot for medical use. But concerns remain about the impact of medical marijuana on teenagers. In a new study published today in The Lancet Psychiatry, researchers found that there was actually no increased use of the drug among youths in the states where laws have been passed for medical marijuana.

Marijuana is the most commonly used illicit drug in the USMarijuana is the most commonly used illicit drug in the US, with widespread use among young people — so it’s surprising that the changes in laws didn’t seem to impact use. In the 21 states where medical marijuana is legal, there was a higher use of marijuana even before laws were passed compared with other states, said Deborah Hasin, professor of epidemiology at Columbia University Medical Center, and lead author on the study. However, there was no increase in rates of adolescent marijuana use after a state legalized the drug for medical use, she explained.

Hasin and her team assessed data from the Monitoring the Future study, which includes information from over 1 million students who were in the eighth, 10th and 12th grades (13–18 years) of 400 schools. Those surveys started in 1991, and the most recent was in 2014. During that time, 21 states passed laws for the use of marijuana for medical purposes; the first being California in 1996, and the 21st state was Maryland last year. (Since the most recent study, Minnesota and New York have also legalized medical marijuana.) Students completed a self-administered questionnaire about any marijuana use in the previous 30 days. The researchers adjusted the data to account for various factors, such as sex, age, race, education of parents, class size, and whether educated at an urban or rural school, public or private school. The study found that 16 percent of teenagers used marijuana in the states where medical marijuana was later legalized, compared with 13 percent of teenagers in the states where there are no such laws. But there was no statistical significant difference between teenage marijuana use before or after the laws were passed.

There was no significant difference between teen marijuana use before and after medical marijuana laws were passedThis study gives the most definitive answer to date on the contentious question of whether medical marijuana laws increase cannabis use among teenagers, Kevin Hill from the Division of Alcohol and Drug Abuse, Belmont, told The Verge.

Early adolescent use of marijuana may have long-term harmful consequences such as altered brain development, cognitive damage, and psychiatric symptoms — and the study authors write that cannabis use in teenagers can impact employment prospects and can result in substance addiction. Policy makers and scientists seem to have widely varying opinions on what legalizing medical marijuana will do for teenagers. Richard Gil Kerlikowske, US Commissioner of Customs and Border Protection and Former Director of the Office of National Drug Control Police, thinks that legalizing medical marijuana will give teenagers the wrong idea: "When I’ve done focus groups with high school students in states where medical marijuana is legal, they say, 'Well, if it’s called medicine, and it’s given to patients by caregivers, then that’s really the wrong message for us as high school students.'"

A 2014 Monitoring the Future study assessing teenage drug use in the US found fewer young people believe marijuana is risky. In this same study high school seniors (age 17 and 18 years) said they would try marijuana or use it more often if it were legalized for general use. And in another survey of teenagers, in states that had not legalized medical marijuana, 55 percent (out of 393 teenagers) thought that passing a law like this would "make it easier for teens to start to smoke marijuana for fun."

A growing body of evidence shows medical marijuana doesn't impact teen drug useBut this new study can be added to a growing body of evidence that actually shows that legalizing medical marijuana does not impact teenage drug use. A recent 2014 study published in the Journal of Adolescent Health looked at data from over 11 million teenagers and found similar findings: there was no statistically significant differences in use of marijuana before or after policy changes were made, although the period looked at for this was shorter (20 years) than this new study.

Medical marijuana research — despite being underfunded, and despite researchers’ difficulties in acquiring study drugs — has suggested benefits for several disorders. The jury is still out, since almost no large clinical trials have been conducted, but a few studies have shown positive effects in conditions including glaucoma and neuropathy. Though the FDA hasn’t approved pot as a safe and effective treatment for any diseases, the agency has indicated it supports further scientific research.

"An easy assumption to make would be that medical marijuana laws would increase access to marijuana, and therefore use among adolescents would increase," said Kevin Hill in an accompanying comment published in The Lancet Psychiatry. "Policies might sometimes be shaped by preconceived notions that do not end up being true."