Nearly 10 percent of American teens say they have tried hashish, according to a new study.
A quarter of teens who have tried marijuana have also used hashish, which contains a greater concentration of THC, the psychoactive ingredient in marijuana.
While a marijuana cigarette has about 0.5 to 5 percent THC, hashish contains between 2 and 20 percent, and sometimes as much as 50 percent, HealthDay reports.
The researchers from New York University's Center for Drug Use and HIV Research analyzed data from more than 10,500 high school seniors.
They found other drug use was a risk factor for hashish use, as was regular cigarette smoking and frequent alcohol use. As the frequency of marijuana use increased, so did the risk for recent hashish use.
Teen girls were at low risk for using hashish, but not for marijuana.
The findings are published in the American Journal of Drug and Alcohol Abuse.
The study used data from the annual Monitoring The Future survey of teens. The most recent Monitoring the Future survey, released in December, found teens are using less marijuana, alcohol and cigarettes. The study found marijuana use among teens declined from 26 percent in 2013 to 24 percent in 2014.