About 1 in 7 U.S. adults reported using marijuana last year, and many believe it has health benefits

Nearly 15 percent of adults in the U.S. reported using marijuana last year, according to a study recently published in the Annals of Internal Medicine journal.

Researchers found that 1 in 7 adults used some form of cannabis in 2017, up slightly from 13 percent in 2016. In states where marijuana is legal for recreational use, the rate of users was as high as 20 percent.

The survey of the 9,003 adults found that Americans have a more favorable view of marijuana than existing scientific evidence supports, the study's authors wrote.

What did the study find?

In states where marijuana is illegal in all forms, only 12 percent of the adults surveyed reported using it.

Thirteen percent of adults in the U.S. reported using pot in 2016, according to a Gallup poll published earlier this month. In 2013, only 7 percent said they used it.

Sixty-six percent of respondents perceived pain management to be the most common benefit of marijuana use, followed by treatment for diseases such as epilepsy and multiple sclerosis (48 percent). Forty-seven percent believed it treats depression and anxiety.

About 91 percent of the people surveyed believe marijuana poses at least one risk. Just over half cited legal problems as the primary risk. Other identified risks included addiction (50 percent) and impaired memory (42 percent).

Nearly 30 percent believe marijuana prevents health problems and 7.6 percent think it's entirely safe for children.

What did the experts say?

The study's co-author Dr. Salomeh Keyhani said he's concerned about the landscape of marijuana, new forms of use, and its higher concentrations of THC, the Daily Mail reported. Keyhani is a professor in the Division of General Internal Medicine at the University of California, San Francisco.

"We don't understand the impact of products with high THC," Keyhani told the Daily Mail.

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

"Historically, the downside of marijuana have been minimized. Its use has been considered safe and without risks and that is not necessarily the case." Dr. Michael Lynch told the Daily Mail. Lynch is the medical director of the Pittsburgh Poison Center of the University of Pittsburgh Medical Center.

He said higher concentrations of THC could cause serious effects.

"When it's more concentrated or more highly potent, you see side effects like agitation," he said. "There's a potential for anxiety and for psychotic effects."

The cognitive risk for younger users is greater.

"Early use is associated with more negative effects on brain and cognitive development," Lynch told the outlet.