In Colorado marijuana is not only legal, it is also apparently pretty darn strong.

New data from Charas Scientific, a lab certified to test the potency of Colorado’s pot, finds that marijuana in the state is roughly three times stronger than it was thirty years ago. In particular, CBS News reports that researchers have found potency values ranging from 20 to 30 percent THC.

THC, or tetrahydrocannabinol, is the psychoactive compound in marijuana that produces the feeling of a “high” in a user’s brain.

The National Institute on Drug Abuse has also seen an increase in marijuana potency over the last few decades. But a level of 20 or 30 percent THC goes far beyond anything the institute has reported in the past. Indeed, in 2012 the institute found that marijuana seized by police agencies nationwide had an average THC concentration of about 15 percent, up roughly 10 percent from the 1980s.

“As far as potency goes, it’s been surprising how strong a lot of the marijuana is,” said Charas Scientific founder and director of research, Andy LaFrate, Ph.D. “We’ve seen potency values close to 30 percent THC, which is huge.”

Researchers speculate that the increased potency of Colorado’s pot may be due to marijuana growers cross-breeding different strains of the plant. A potential side-effect of cross-breeding, however, is a decrease in the levels of  cannabidiol. Cannabidiol is a compound in pot scientists have linked to several potential medicinal uses, including treating Alzheimer’s and Huntington’s disease, as well as conditions like seizure disorders, anxiety and schizophrenia.