As a growing number of states legalize marijuana in the US, a new poll has found that 1 out of 7 Americans used marijuana in the past year.

New survey results published in the “Annals of Internal Medicine” found that more Americans are using marijuana, for both medical and recreational use, with smoking being the most common form of consumption.

20% of those living in a state where recreational use is legal used marijuana in the past year compared to just 12% percent in states where it was completely illegal.

The poll found that people in the US are more likely to consume marijuana through vaping or as an edible in states that have legalized for recreational use. The survey was national in scope and polled 16,280 US adults.

Overall, 8.7% said they had used cannabis in the past 30 days while 14.6% of respondents reporting using in the past year. More of those living in a state where recreational used is legal (20%) used cannabis in the past year than those who lived in states where it’s totally illegal (12%).

Of those living in states where medical marijuana is legal, 14% percent of people said they had used the drug in the past year (12.9% smoking, 6% consuming edibles, 4.7% vaping, 1.9% using concentrates, and 0.8% using topical cannabis).

Also worth noting is that marijuana use was related to age. Younger people were more likely than older people to use marijuana, with people between 18 and 34 reporting the highest use (smoking was most common — 55%).

The study’s author raised concerns about the findings and their implications.

“There are increasingly novel forms of marijuana available and the risks of these products to health are unknown,” said study author Dr. Salomeh Keyhani of the University of California, San Francisco. “THC (the psychoactive component) is very high in some forms of marijuana. We don’t understand the impact of products with high THC.”

The study also took issue with more states voting to legalize marijuana and cannabis and the rapid commercialization of the recreational drug.

“It seems like the current regulatory structure is not keeping pace with commercialization,” said Keyhani. “There is commercialization without uniform standards on the types of products that can be sold or marketed to the public.”