New York state legislators and Gov. Andrew Cuomo have approved a law allowing recreational use, production and sale of marijuana for people over age 21. State Sen. Liz Krueger, a Democrat from Manhattan, has long sponsored legislation to legalize marijuana. During the Senate debate, she said: "In fact, the data coming in from some states that have legalized marijuana is that they actually see a decrease in use over time, particularly among young people."

Given concerns about whether young people will be more inclined to use marijuana, even if it is legal only for people age 21 and older, we wondered if reliable data supported Krueger’s point. 

We reached out to Krueger’s office, and a spokesman, Justin Flagg, sent us several studies. 

In Colorado, the legal sale of recreational marijuana began in 2014. Four years later, Colorado’s Division of Criminal Justice published a study about the effects of legalization, and found that between 2005 and 2017 the proportion of Colorado high school students reporting using marijuana ever in their lifetime had modest fluctuations but remained statistically unchanged. Also, the study found no statistically significant difference between Colorado student responses compared to national data. The proportion of students reporting they had used marijuana in the last 30 days was also stable, with no significant changes, from 2005 to 2017. 

A year after that report, the Healthy Kids Colorado Survey found that youth marijuana use had ticked up slightly from the previous survey, and was up less than 1 percentage point from just before legal sales began. Survey authors reported there had been no significant change since 2005. 

Other studies also suggested no change in youth use in Colorado. In 2018, a study in Prevention Science showed that for high school students there were no significant changes in marijuana use when they were asked if they had used it ever, or in the last 30 days.  

In Washington state, which legalized recreational marijuana in 2012, a study from the Rand Corp. and others published in JAMA Pediatrics in 2018 found a small decrease in youth use, but warned that more data is needed to identify long-term trends. Marijuana use dropped a small, but statistically significant amount among eighth graders and 10th graders in Washington state following legalization, in 2014 and 2016, compared with 2010 and 2012, researchers wrote. Among eighth graders, prevalence of marijuana use fell from 9.8 percent to 7.3 percent. Among 10th graders, use fell from 19.8 percent to 17.8 percent. No changes were reported among 12th graders.

A 2019 study in the American Journal of Drug and Alcohol Abuse found that there were not significant shifts in use among youth overall in places that had decriminalized marijuana, "but predicted significant declines in marijuana use among 14-year olds and those of Hispanic and other ancestry (1.7-4.4 percentage points), and significant increases among white adolescents (1.6 percentage points)."

In a research letter published in JAMA Pediatrics in 2019, researchers wrote that based on their analysis of surveys in states that had legalized recreational adult-use marijuana, youth use "may actually" decline. Recreational marijuana laws were associated with an 8 percent decrease in the likelihood of marijuana use and a 9 percent decrease in the likelihood of frequent marijuana use.   

Study author D. Mark Anderson, an associate professor of economics at Montana State University, told PolitiFact earlier this year that researchers interpreted their results as consistent with the argument that as licensed dispensaries that require proof of age replace drug dealers, marijuana becomes more difficult for teens to obtain.    

We talked to three academic researchers who study marijuana legalization, and they all said that there is not a definitive link between legalization and lower use by minors. 

Magdalena Cerda, an associate professor at New York University Grossman School of Medicine, was a co-author of the Rand study. That study found a decrease in adolescent marijuana use after legalization, but it didn’t have a comparison group, therefore it’s unclear whether the decrease was due to legalization, or whether, in the absence of legalization, the decrease would have been larger, Cerda said.

Another of Cerda’s studies, published in 2019 in JAMA Psychiatry, found no change in use among adolescents, but a potential small increase in cannabis use disorder, particularly among adolescents who had previously used marijuana. Based on the JAMA Psychiatry study and the JAMA Pediatrics study, Cerda said, "I think this suggests that we don’t see an increase in use among the general population of adolescents in the short-term aftermath following legalization." As for problematic use among existing users, the finding is very preliminary and requires further study, she said.     

Katharine Neill Harris, a fellow in drug policy at the Baker Institute for Public Policy at Rice University, said that youth use has been on a decline since the early 2000s, before any state legalized recreational marijuana. In looking at youth use since legalization, Colorado’s data is best, and that it shows that marijuana use by high school students has been stable, she said. 

Featured Fact-check

Andrew Cuomo

stated on April 11, 2018 in a conversation with reporters

"I think we're actually ahead" on legalizing marijuana for recreational use in New York state.

In states that have legalized, increases or decreases have been very small, Harris said. Meanwhile, among adults, marijuana use is increasing nationwide, including in states that have legalized, she said.

She pointed us to a study published in July 2020 from the University of Washington, which showed that reductions in teen use could be slowed by legalization, meaning that teen use could have decreased more without legalization. The Washington study followed a smaller group of young people over time, which offers a different analysis than point-in-time survey data from a larger group. 

It’s still too early to make any definitive conclusions about whether legalization impacts youth use, she said.  

Jonathan P. Caulkins, a past co-director of the Rand Drug Policy Research Center and a professor at Carnegie Mellon University, said there are 15 states and multiple indicators from which advocates can pick statistics. The overall finding, Caulkins said, is that legalization for adults was accompanied by stable rates for youth overall, but youth rates of risky behaviors such as smoking, drinking, getting drunk, and other indicators are all down. "Some of us guess that legalization has offset or erased what otherwise would have been progress," he said. 

Still, the effect of legalization is small, if any, he said. The reasons for this are that legalization was only for adults, not kids, and that marijuana was already widely available even where it was prohibited and that in many states, legalization came after medical marijuana was permitted in brick and mortar stores, broadening legal access. 

"It has been less bad for kids than we feared it might be, and it is definitely not bad and might even be level, but it is just not right to say that a fair and comprehensive look at the data concludes that kids have been helped by legalization in that way," Caulkins said.  

PolitiFact has fact-checked similar claims. 

In 2019, PolitiFact found that adult use in Colorado through 2017 rose, as it had been trending before legalization, while youth use remained the same or decreased a little.  

Also in 2019, PolitiFact Illinois rated a claim that "steady decreases in youth use" in states that have legalized Mostly False, based on a lack of evidence from states that have legalized. 

In March, PolitiFact Wisconsin issued a Half True ruling to a claim that youth usage has gone down in states that have legalized, citing the JAMA Pediatrics study and other sources. 

Krueger said data from "some states" that have legalized shows a decrease in use over time, particularly among young people. 

The data shows youth usage has been stable, or with a decrease according to some research. Other research has shown, meanwhile, that legalization could actually thwart a downward trend in youth usage, and that problematic use among teens could increase after legalization. 

Krueger’s statement could leave the listener with the impression that there is a relationship between legalization and lower rates of youth marijuana usage.

Some research might support this, but certainly not all of it, and researchers warn that more study is necessary.  

We rate this Half True.