Marijuana being grown today is much more potent than marijuana grown 20 or 30 years ago, according to a study by a Colorado-based lab.

“I would say the average potency of marijuana has probably increased by a factor of at least three. We’re looking at average potencies right now of around 20 percent THC,” said Charas Scientific lab founder Andy LaFrate, PhD. He presented his findings this week at the annual meeting of the American Chemical Society.

THC is the psychoactive compound in marijuana that produces the feeling of being high.

“As far as potency goes, it’s been surprising how strong a lot of the marijuana is,” said LaFrate. “We’ve seen potency values close to 30 percent THC, which is huge.”