The number of American adults who smoke marijuana has increased by 10 million.
More Americans are using marijuana, and fewer people think that regularly doing so is harmful.
The new study shows that from 2002 to 2014, the number of American adults who used marijuana in the last year increased by 10 million and the number of people who used it daily increased by more than four million. More adults also started using marijuana for the first time. Yet there was not an increase in reported marijuana abuse or dependence.
The study, which was published in the The Lancet Psychiatry, surveyed over 50,000 adults between the years 2002 and 2014. Interestingly, the researchers also observed a drop—50% to 33%—in the number of people who thought that smoking marijuana once or twice a week was harmful.
The researchers note that the change in how people thought about and used marijuana happened in 2007. At that point, 12 states in the U.S. had legalized medical marijuana use. Policy changes may have impacted the number of people who use marijuana and how the public perceives it, the researchers argue.
“I hope my medical colleagues will start inquiring of their adult patients if they are using marijuana because it could interact with other medications or treatments,” says study author Dr. Wilson Compton of the National Institute on Drug Abuse. “The fact that people are using it on a regular basis means the public health community needs to be paying attention.”
The study authors write that there should be prevention efforts to “target the reduction in perceived harm of using marijuana.” They add that heavy marijuana use was associated with unemployment, lower-than-average income, diminished life satisfaction and criminal behavior, though it wasn’t shown that marijuana caused those issues.
Other researchers are keen to study the effects of marijuana and argue that it’s safe and has much potential for medicinal uses, like for pain treatment, anxiety, Alzheimer’s disease and more.
This article originally appeared on Time.com.