Legalization Doesn’t Increase Problematic Marijuana Use

A new study concludes that state marijuana legalization laws are not associated with increases in “problematic” cannabis consumption or with more impulsive behaviors.

“The results indicated that participants’ problematic cannabis use and impulsivity was not different whether they resided in states where cannabis is legal for medical and/or recreational use or prohibited,” the researchers, who are from several universities in Australia, wrote.

The peer-reviewed paper did find that frequent marijuana consumption itself is associated with impulsivity, but that changing U.S. state laws to allow such use does not lead to an increase in problematic behaviors.

“Our results also show that legalisation status in the USA is not associated with problematic cannabis use and impulsivity.”

“The current findings go beyond prior studies to suggest that, at this point in time, the legalisation status of cannabis has not shown an association with cannabis use amongst frequent users, a finding supported by a growing body of literature,” reads the study, which was published online last month in the journal Drugs In Context. “Although the detrimental health effects of frequent cannabis use are well established, our findings suggest that legalisation status does not worsen these effects.”

The results were culled from online surveys filled out by 329 frequent marijuana consumers, defined as having used cannabis once or more per week for the past 12 months. The responses of those who live in a state with legalization were then compared to those from people in states with ongoing prohibition.

“The interaction between impulsivity and legalisation status was not significant in both models suggesting that the relationship between impulsivity and problematic cannabis use was not different depending on legalisation status,” the study concluded.

The new results come as a growing body of other research shows that state legalization policies are not associated with increased youth marijuana use.

For good reason, there’s a lot of interest in tracking marijuana use trends in the era of legalization, especially as it concerns youth consumption.

Thankfully, there’s been a great deal of research examining these trends—and a meta-analysis published this week in the journal Current Addiction Reports took a holistic look at the existing scientific literature to learn about the prevalence of cannabis use post-legalization.

Fifty-five studies were included in the new analysis.

Just as numerous prior studies have concluded, the researchers found that adolescent marijuana use does not increase after a state legalizes cannabis. Further, reports of higher rates of marijuana use among teenagers in legal states ignores the fact that those rates were generally higher before the passage of medical cannabis laws, the researchers explained.

Still, the studies “suggest that passage of [medical marijuana laws] has not increased cannabis use among teenagers during the periods after their passage that has been studied to date,” the researchers wrote.

For adults, the story is somewhat different. The frequency of marijuana consumption among adults has increased in states where medical cannabis has been legalized. However, that increase generally applies to adults who reported using cannabis prior to the implementation of a medical marijuana program.

The meta-analysis also looked at rates of cannabis use disorder in states that have ended prohibition. The assumption, as the researchers wrote, would be that higher rates of marijuana consumption among adults would mean higher rates of cannabis use disorder. Turns out, that wasn’t the case:

“Despite the increase in the prevalence of adult cannabis use, the prevalence of cannabis use disorders among adults in the past year did not change (remaining at 1.5 percent [from 2002 to 2004]). More surprisingly still, the prevalence of [cannabis use disorder] among adults who used cannabis in the past year declined from 14.8 percent in 2002 to 11.0 percent in 2014.”

There are a couple of theories the researchers floated to explain this trend. It could be a reflection of the fact that the rate of underage marijuana use has declined, and that age group is generally more prone to developing a cannabis use disorder, for example.

In any case, the main takeaways from the meta-analysis are pretty cut and dry: adolescents really aren’t using marijuana more frequently in states that have legalized, adults who were current users before a state legalized ended up consuming more post-legalization and cannabis use disorder doesn’t seem to be increasing even as more states opt to liberalize their marijuana laws.

Meta-analyses are helpful, the researchers wrote, because they can “potentially detect weak effects that may not be present in all or any of the individual studies.” In the case of this meta-analysis, however, “the results supported the findings of the individual studies.”