Legalization boosts marijuana use in big way, study of twins reveals

BOULDER, Colo. — Legalizing marijuana appears to promote more use among locals, according to a new study focusing only on pairs of adult twins. Those living in a legalized state report using cannabis 20 percent more often in comparison to their twin residing in a state where recreational use is still illegal.

Similarly, when considering all participants in the study, residents in states with legalized marijuana use it 24 percent more frequently than the residents of states that prohibit marijuana use. Conducted by scientists at University of Minnesota and University of Colorado, this study of 3,400 twins is some of the most compelling work to date indicating that legalization causes increased use. On a relate note, marijuana use in general is on the rise in the United States – including among adults.

“Across America, there is a trend toward using more marijuana but we found that the change is bigger in states where it is legal,” says lead study author Stephanie Zellers, a recent University of Minnesota graduate who began the research while a PhD student at CU Boulder’s Institute for Behavioral Genetics (IBG), in a university release.

Researchers analyzed data from two large longitudinal twin studies to reach these conclusions. Those projects tracked pairs of twins, residing in either Colorado or Minnesota, from childhood. The team asked each participant how often they used marijuana both before and after 2014. That’s when Colorado became one of the first states to start selling legal recreational marijuana. Meanwhile, recreational marijuana still isn’t legal in Minnesota.

Prior to 2014, the two states showed little differences in cannabis use. However, that changed after 2014. Across all participants, those living in Colorado used cannabis 24 percent more frequently than others living in Minnesota.

Could more marijuana use have some positives?

Regarding identical twin pairs specifically, those living in a legalized state used marijuana 20 percent more often. Since twins share their genes, typically grow up in the same socioeconomic bracket, and share parental influences as well as community norms, they served as ideal research subjects, study authors explain. By studying twins, the research team was able to minimize alternative explanations for their findings.

“This is the first study to confirm that the association between legal cannabis and increased use holds within families in genetically identical individuals,” explains study co-author John Hewitt, a professor in the Department of Psychology and Neuroscience and faculty fellow at IBG. “This makes it much more likely that legalization does, in itself, result in increased use.”

Today, over 141 million Americans reside in a state with recreationally legal marijuana. Per the National Institute on Drug Abuse, cannabis use among young adults (ages 19-30) has never been higher; 43 percent report using in the past year and 29 percent in the last month.

“Typically, what we would expect to see is that people tend to increase use as adolescents and then reduce it as they transition into adult roles, family life and stable jobs,” Zellers adds. “Interestingly, we saw escalation, not reduction, in adults.”

Study authors note it is highly unlikely that legalization alone would lead to those who abstained from marijuana before to suddenly start indulging after. Additionally, early results from their broader ongoing research project indicate increased use may not necessarily be a bad thing.

“In other analyses, we are finding that this increased use is not accompanied by increased problems, may be associated with less alcohol-related problems, and otherwise does not, in general, seem to have adverse consequences,” Prof. Hewitt concludes.

The study is published in the journal Addiction.

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  1. Contrary to what prohibitionists are so desperately trying to get the public to believe wholeheartedly and without question, legalizing marijuana IS NOT adding anything new into our society that wasn’t always there and widely available already.

    Therefore marijuana legalization does not lead to some massive influx of new marijuana consumers. The very same people who have been consuming marijuana during it’s prohibition are for the most part the very same ones who will be consuming marijuana when it’s legal.

    The prohibition of marijuana has never prevented marijuana’s widespread availability nor anyone from consuming marijuana that truly desires to do so.

    Marijuana has been ingrained within our society since the days of our founding fathers and part of human culture since biblical times, for thousands of years.

    So, since marijuana has always been with us and humans already have thousands upon thousands of years worth of experience with marijuana, what great calamities and “Doomsday Scenarios” do prohibitionists really think will happen now due to current legalization efforts that have never ever happened before in all human history?

    There is absolutely no doubt now that the majority of Americans want to completely legalize marijuana nationwide. Our numbers grow on a daily basis.

    The prohibitionist view on marijuana is the viewpoint of a minority and rapidly shrinking percentage of Americans. It is based upon decades of lies and propaganda.

    Each and every tired old lie they have propagated has been thoroughly proven false by both science and society.

    Their tired old rhetoric no longer holds any validity. The vast majority of Americans have seen through the sham of marijuana prohibition in this day and age. The number of prohibitionists left shrinks on a daily basis.

    With their credibility shattered, and their not so hidden agendas visible to a much wiser public, what’s left for a marijuana prohibitionist to do?

    Maybe, just come to terms with the fact that Marijuana Legalization Nationwide is an inevitable reality that’s approaching much sooner than prohibitionists think, and there is nothing they can do to stop it!

    Legalize Nationwide!…and Support All Marijuana Legalization Efforts!

  2. The very last paragraph has all of the important information… where most people will never read to that point. Alcohol abuse decreased in states where weed is legal. The twins in the weed legal states were less likely to drink and drive. And there were no *gotcha* findable ill effects to the weed legalization, including NO increase in other illicit drug use. Gateway drug? Pretty ineffective as a gateway drug. Alcohol is the real gateway drug. At least we have up on prohibition on that, after the disastrous results. The federal government needs to repeal prohibition of Marijuana, now. It was primarily the illegalization of weed that drove the militarization of the US police. Waaay more people partake in weed than other illegal drugs. The theory of a “gateway drug” is that it increases the probability of becoming a hard-core drug addict, like a meth head or a crack smoker or a heroin/opiod addict. This study shows there is NO increase in illicit drug use associated with legalized weed.

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