More adults use marijuana in states where it is legal

November 13, 2017, Columbia University's Mailman School of Public Health
Credit: CC0 Public Domain

Daily use of marijuana as well as past month rates rose for both men and women aged 26 and older in states with medical marijuana laws in effect, according to researchers at Columbia University's Mailman School of Public Health. Marijuana use among those younger than 26 years old was generally unaffected by changes in the law. The results of the study are published online in Prevention Science.

In states with , daily marijuana use for male users age 26 and older increased from 16.3 percent to 19.1 percent, and for women, from 9.2 percent to 12.7 percent. Past month use among men in the same age bracket increased from 7.0 percent before the laws passed to 8.7 percent following their passage, and for women rose from 3.0 percent before to 4.3 percent after. There were no significant increases in past-year marijuana use disorder (continuing to use despite significant behavioral or psychological changes) for any age or gender group following passage of the laws.

The study also documents a rise in males ages 18-25 using marijuana daily compared to females. "Among past month users, more than one in five young men ages 18-25 living in states with medical marijuana laws said they used marijuana every day," said Christine Mauro, PhD, assistant professor of Biostatistics at Columbia's Mailman School of Public Health, and first author.

Daily use was generally higher among individuals aged 18-25 compared with those ages 12-17 and those 26 or older, regardless of their state's laws around marijuana. "Daily marijuana use raises as the brain doesn't fully mature until age 25," noted Mauro.

The researchers analyzed state-level survey data from the National Survey on Drug Use and Health for the years 2004-2013, including more than 17,500 youth (12-17 years-old), 17,500 young adults (18-25 years-old), and 18,800 adults 26 and older per year studied.

Since 1996, more than half of the United States has passed medical marijuana laws, with 28 states legalizing medical marijuana use as of November 2016; eight states have legalized recreational marijuana. "As more states enact laws and more years of data are available, future research should examine how legalization of recreational marijuana and other local rules contribute to changes in marijuana use," said Mauro.

Rising rates of marijuana use raises concerns regarding associated increases in heavy use of marijuana and marijuana use disorder. Earlier research by Columbia researchers estimated that 16.2 percent and 57.2 percent of daily marijuana users meet criteria for DSM-IV abuse and dependence diagnosis, respectively.

"The advent of medical marijuana laws has been proposed as one potential cause of the increased prevalence of marijuana use, but there is now a general consensus that passage of the laws has not affected rates of use in adolescents," said Silvia Martins, MD, PHD, associate professor of Epidemiology at the Mailman School, and senior author. Until this most recent data, studies by Martins and colleagues found past-year individual use rose among all adults 26+ in states with medical marijuana laws but had not investigated changes in daily marijuana use and marijuana use disorder.

In fact, despite concerns regarding increased use of pot and enactment of marijuana laws, some positive outcomes have been associated with the laws, including decreased opioid use and decreased alcohol consumption—the latter tied to declining rates of traffic injury fatalities at the state level. "Research shows the impacts of medical marijuana law, both positive and negative," noted Martins.

"Because most in our sample more recently passed medical marijuana laws, it is possible that not enough time has elapsed to observe more significant changes in marijuana use disorder across age-gender subgroups," said Mauro. "Given the impact the disorder may have on individuals, families and society, marijuana use should continue to be monitored regularly. Building the evidence base by age and gender is critical in helping public health professionals better understand which groups, may be most affected by medical laws and target public health programming accordingly."

Explore further: No uptick in marijuana use by adolescents after states pass medical marijuana laws

Related Stories

No uptick in marijuana use by adolescents after states pass medical marijuana laws

October 19, 2016
Adults over the age of 25 increased their use of marijuana after their home states made changes to medical marijuana laws, according to new research by scientists at Columbia University's Mailman School of Public Health. ...

Rates of marijuana use, heavy use, and cannabis use disorder depend on where you live

June 15, 2017
Adult marijuana use rose significantly in states that passed loosely regulated medical marijuana laws (MMLs) according to a new study by Columbia University's Mailman School of Public Health and Columbia University Medical ...

Do medical marijuana laws promote illicit cannabis use and disorder?

April 26, 2017
Illicit cannabis use and cannabis use disorders increased at a greater rate in states that passed medical marijuana laws than in other states, according to new research at Columbia University's Mailman School of Public Health ...

States with medical marijuana laws see drop in prescriptions

April 28, 2017
(HealthDay)—Medical marijuana laws are associated with a decline in the number of prescriptions filled for Medicaid enrollees, according to a study published in the April issue of Health Affairs.

Since passing medical marijuana laws, states have seen lower numbers of fatal car crashes involving opioids

September 15, 2016
A study conducted at Columbia University's Mailman School of Public Health found that there were fewer drivers killed in car crashes who tested positive for opioids in states with medical marijuana laws than before the laws ...

Study finds up to one-quarter of cancer patients use marijuana

September 25, 2017
A new study conducted in a cancer center in a state with legalized medicinal and recreational marijuana found that approximately one-quarter of surveyed patients used marijuana in the past year, mostly for physical and psychological ...

Recommended for you

Smoking linked with higher risk of type 2 diabetes

March 15, 2018
The prevalence of diabetes has increased almost 10-fold in China since the early 1980s, with one in 10 adults in China now affected by diabetes. Although adiposity is the major modifiable risk factor for diabetes, other research ...

Key drivers of high US healthcare spending identified

March 13, 2018
The major drivers of high healthcare costs in the U.S. appear to be higher prices for nearly everything—from physician and hospital services to diagnostic tests to pharmaceuticals—and administrative complexity.

Pedometer health boost lasts four years

March 13, 2018
Wearing a pedometer to count your daily steps can keep you healthier and more active for as long as four years after using it, a new study shows.

Toilet-to-tap: Gross to think about, but how does it taste?

March 13, 2018
Here's a blind test taste like Pepsi never imagined. Researchers at the University of California, Riverside, recently published a study of recycled wastewater that did not focus on its safety-which has long been established-but ...

The Great Recession took a toll on public health, study finds

March 12, 2018
The Great Recession, spanning 2008 to 2010, was associated with heightened cardiovascular risk factors, including increased blood pressure and glucose levels, according to a new UCLA-led study. The connections were especially ...

Lead poisoning may hasten death for millions in US: study

March 12, 2018
Persistent, low-level exposure to lead over decades is statistically linked to some 400,000 premature deaths in the United States each year, far more than previously thought, researchers said Monday.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.