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Study Shows 20% Increase in Frequency of Cannabis Consumption in Recreational States

The journal published a new study AddictionOn Aug. 24, the National Cannabis Consumption Data Analysis Center focused on identical twins and adult cannabis use data. Called “Impacts of recreational cannabis legalization on cannabis use: a longitudinal discordant twin study,” the study used twins to explore the frequency of cannabis across two different states.

“In this study, we evaluated the effects of recreational cannabis legalization in a large sample of prospectively assessed adult twins from similar cohorts of individuals born in Colorado and Minnesota, demographically similar states with different cannabis policies,” the researchers presented in their introduction. “While many participants still reside in their birth states, some participants have migrated to other states resulting in pairs discordant for exposure to recreational legalization.”

The data was gathered from the University of Colorado Boulder Center for Antisocial Drug Dependence or the Minnesota Center for Twin Family Research. There were a total of 3452 people (split between 1 700 individuals in Minnesota and 1 752 in Colorado). Each individual had been previously questioned about their use of cannabis before 2014, when Colorado legalized recreational cannabis and Minnesota legalized medicinal cannabis. This number was split into three types of twins, monozygotic (363 couples), same-sex bizygotic (208) and opposite-sex trizygotic (122 pairs).

The researchers concluded that in 111 pairs of twins, there were no genetic influences that led to cannabis consumption frequency, however they did confirm that “Existing genetic influences were moderated by the legal environment, as the genetic correlation between marijuana use before and after legalization was lower in states that legalized compared with states that did not.”

“Using a longitudinal design accounting for age, sex and earlier cannabis use, we found a ~24% increase in mean cannabis use frequency attributable to legalization,” researchers explained. “Furthermore, co-twin control results indicate that within monozygotic pairs, the twin living in a legal state uses cannabis ~20% more frequently than their illegally residing co-twin.”

Researchers also pointed out that 92% were white, and they projected changes in the results if there was more of them. “An important extension of our work would be to investigate individual differences in the context of cannabis policy with respect to sex or racial background. Prior to recreational legalization, black Americans disproportionately bore the consequences of cannabis law enforcement,” researchers wrote. “Racial disparities in pre-legalization enforcement could mean that the legalization-related environmental changes experienced by black Americans were more dramatic than those experienced by their white counterparts, but we are not able to address this issue effectively in these samples.”

The researchers concluded that the topic needed more investigation to better understand the impact of marijuana on other people. “Through the use of zygosity-stratified co-twin control analyses, we found a ~20% increase in cannabis use frequency, consistent with a causal effect of recreational legalization,” they wrote. “These results do not, by themselves, demonstrate how more frequent use in legal states translates to changes in health or behavioral consequences, therefore future work is necessary to further address complex questions around the public health impacts of legalization and vulnerability to widely available marijuana.”

A new National Institutes of Health study found that cannabis consumption and hallucinogens are at an all time high among people aged 19-30. Researchers said that consumption in this age group has “increased significantly in 2021 compared to five and 10 years ago,” and is the highest level of consumption since 1988.

National Institute on Drug Abuse Director Nora Volkow said in an accompanying statement that this research is crucial to understanding the long-term effects of cannabis on youth. “As the drug landscape shifts over time, this data provides a window into the substances and patterns of use favored by young adults. We need to know more about how young adults are using drugs like marijuana and hallucinogens, and the health effects that result from consuming different potencies and forms of these substances,” Volkow said. “Young adults are in a critical life stage and honing their ability to make informed choices. Understanding how substance use can impact the formative choices in young adulthood is critical to help position the new generations for success.”