By Linda Carroll

(Reuters Health) – With more and more states legalizing marijuana, whether for medical use, recreational use, or both, increasing numbers of Americans are using cannabis. A new survey finds that one in seven had used marijuana in 2017, with smoking being the most common manner of consumption, according to a report published in the Annals of Internal Medicine.

People were more likely to vape or to consume marijuana as an edible in states where recreational use has been legalized, researchers found in the nationally representative survey of 16,280 U.S. adults.

Overall, 14.6 percent said they had used cannabis in the past year, while 8.7 percent said they had used the drug in the past 30 days. A greater proportion of people, 20 percent, reported using marijuana in the past year if they lived in a state where recreational use was legal, as compared to just 12 percent in states where it was completely illegal. In states where medical marijuana was legal, 14 percent of those surveyed said they had used in the past year.

While 12.9 percent reported smoking marijuana, 6 percent said they had consumed edibles, 4.7 percent reported vaping, 1.9 percent said they had used concentrates and 0.8 percent reported using topical versions of cannabis.

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

Keyhani is concerned about the rapidly changing landscape. “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.”

Cannabis use was inversely related to age. Younger people were more likely than older ones to use, with those between 18 and 34 reporting the highest use.

Smoking was the most common form of cannabis use, at 55 percent.

Baked goods or pastries and candy were the most common forms of edibles consumed by U.S. adults.

Keyhani is right to be concerned about the varying levels of THC in the cannabis products people are using, said Dr. Michael Lynch, an emergency physician and toxicologist and medical director of the Pittsburgh Poison Center of the University of Pittsburgh Medical Center.

“Historically the downsides of marijuana have been minimized,” Lynch said. “Its use has been considered to be safe and without risks and that is not necessarily the case. For example, 10 percent of adult users become addicted, while about 17 percent of adolescent users do. Those are not insignificant numbers when you consider that the overall numbers are increasing.”

What’s most concerning, Lynch said, are products with high concentrations of THC, whether it’s in oils for vaping or in edibles. “When it’s more concentrated or more highly potent, you see side effects like agitation,” he added. “There’s a potential for anxiety and for psychotic effects.”

And while there’s talk about cannabis calming seizures, in high potency forms it can actually bring them on in people who are vulnerable, Lynch said.

Lynch is also concerned about teen use. “Early use is associated with more negative effects on brain and cognitive development,” he said.

Ultimately, there needs to be more research on cannabis, and a way to know what potency marijuana you’re getting, Lynch said.

“In states like Pennsylvania, where medical marijuana is legal, it’s tightly regulated in terms of concentrations,” he said. “So what’s on the label ought to be correct.”

As for risks and benefits, that’s “a moving target,” Lynch said.

SOURCE: Annals of Internal Medicine, online August 27, 2018.