(Reuters Health) – In the four states where recreational marijuana was legal by 2016, there was a small uptick in cannabis use disorder among adults and teens, and a general rise in use by adults, a new study suggests.
Researchers looking at data on cannabis use between 2008 and 2016 found that rates of problematic use among teens and adults over age 26 rose faster in states where recreational marijuana had been legalized than in other states, according to the report published in JAMA Psychiatry.
“Other studies have looked at the effect of medical marijuana legalization,” said the study’s lead author Magdalena Cerda, an associate professor in the department of population health and director of the Center for Opioid Epidemiology and Policy at NYU Langone Health in New York City. “But this is the first national study to look at the impact of legalization of recreational marijuana use. This is a really important piece in helping us understand how to legalize it in a way that puts systems in place that will deal with the prevention and treatment of marijuana use disorder.”
Although the study showed an increase in problematic use, “I don’t think these findings suggest states shouldn’t legalize cannabis,” Cerda noted. “Obviously there are lots of benefits. But we have to pay attention to how it should be regulated to prevent public health harms.”
To look at the impact of legalization, Cerda and her colleagues turned to the National Survey on Drug Use and Health (NSDUH), which each year collects data on more than 17,500 adolescents aged 12 to 17, as well as 17,500 young adults aged 18 to 25 and 18,800 adults aged 26 and older. The survey used audio-based, computer-assisted self-interviews to reduce concerns about confidentiality.
Recreational marijuana was legalized in four states during the study period: in Colorado and Washington in 2012, and in Alaska and Oregon in 2015. In total, researchers looked at data from 505,796 survey respondents.
When the study team compared states where recreational use was legal to those in which it was not, they found overall use and use disorder rose more in the states where marijuana was legal.
Frequent use was defined as 20 days or more of use in the past month. Cannabis use disorder, or problematic use, was defined by answers to a series of questions that indicate “tolerance and dependence and encroaching problems