A new survey by Arizona state university found that a highly potent form of marijuana is being used more than previously thought.
Nearly a quarter of teens surveyed say they've tried marijuana concentrate, which has about 3 times as much THC - the compound which causes a high - than traditional marijuana.
Higher doses of THC have been linked to addiction, impaired thinking, and mental breakdowns.
And researchers say the teens using the concentrate have more risk factors for addiction, such as failure in school or parents who also had substance abuse issues.
Overall, a third of the students said they'd tried some form or marijuana.
The findings come from the 2018 Arizona Youth Survey, a survey of secondary school students done every two years.