(Reuters Health) - Adolescents who try marijuana are not just smoking it. Many are also vaping or eating cannabis, a U.S. study suggests.

Almost one in three teens have smoked cannabis at least once, the survey of 3,177 Los Angeles high school students found. More than one in five adolescents have consumed edible cannabis, and more than one in 10 have vaped it.

In the study of 10th-graders, two-thirds of teen cannabis users had tried at least two forms of the drug, and about 8 percent had tried all three methods of consuming cannabis.

“This raises the question whether teens who have traditionally been at lower risk for use of cannabis and other drugs in traditional smoked forms may be drawn into cannabis in alternative forms that may lack some of the deterrents . . . like the smell, taste, and harshness of inhaling cannabis smoke and difficulty concealing use of smoked cannabis to authority figures,” said senior study author Adam Leventhal, director of the University of Southern California’s Health, Emotion, and Addiction Laboratory in Los Angeles.

Cannabis use during adolescence has been linked to learning and memory deficits as well as impaired academic achievement in previous research. Vaping has also been tied to breathing problems as well as heart and blood vessel damage.

While edible forms of cannabis have been around for decades, these products have become more widely available and acceptable to many teens as a growing number of U.S. states have legalized marijuana for medical and recreational use.

At the same time, increased availability of e-cigarettes that heat cannabis have also become more common, along with cannabinoid-infused e-cigarette liquids in youth-orientated flavors like bubble gum and marketing campaigns that might attract adolescents, researchers note in JAMA Network Open.

In the current study, researchers asked students at 10 Los Angeles high schools in 2015 about lifetime and prior-month cannabis use.

Over the previous month, about 13 percent of participants had smoked cannabis, 8 percent had eaten it and 5 percent had vaped it.

When it came to ever-use of these three methods, students were about four times more likely to have smoked cannabis than to have eaten it, and nearly two and a half times more likely to have eaten it than vaped it, the analysis found.

Boys were more likely than girls to report vaping cannabis but there were no meaningful differences between the sexes for smoking or eating the drug.

Low-income students were more likely to smoke or eat cannabis than their more affluent classmates, but there wasn’t a meaningful income-based difference for vaping.

The study wasn’t designed to prove whether or how any specific demographic factors might directly affect teens’ choice to use cannabis or what forms of the drug they tried.

The surveys were also conducted before the state of California’s legalization of recreational cannabis sales, the authors note.

Still, legalization of marijuana is likely sending the wrong message to parents and teens alike, said Dr. Ellen Rome, head of the Center for Adolescent Medicine at Cleveland Clinic Children’s in Ohio.

“Legalization normalizes use with an illusion of safety for both adults and kids,” Rome, who wasn’t involved in the study, said by email. “Legal for adults means ‘okay to use now’ to the average adolescent marijuana user.”

Parents should make sure teens understand the very real health risks associated with cannabis use during a period in life when their bodies and brains are still developing, Rome said. This is especially true when teens vape cannabis.

“Vaping was heralded as the way to deliver nicotine or other substances while decreasing the toxins associated with smoke inhalation,” Rome said.

“Unfortunately, the flavors used in vaping can cause irreversible small airway damage, a fact (not appreciated by) most adolescent users who do not yet have abstract thought, or the ability to foresee consequences,” Rome added. “That lack of abstract thought also leads teens to not concern themselves with risk of cancer when smoking cigarettes, marijuana, or any other potential toxin.”

SOURCE: bit.ly/2Qppup9 JAMA Network Open, online September 28, 2018.