CBD may protect against psychiatric risk from high-THC cannabis strains

A study reported Sept. 5 by neuroscientists at Indiana University finds that a non-psychoactive compound in cannabis called cannabidiol, or CBD, appears to protect against the long-term negative psychiatric effects of THC, the primary psychoactive ingredient in cannabis.

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Other research has shown that long-term use of cannabis increases adolescent drug users' risk for certain psychiatric and neurological disorders, such as schizophrenia. The risk to teens is greater than ever since selective breeding of plants to produce higher levels of THC over the past several decades has substantially increased exposure to the compound.

"This study confirms in an animal model that high-THC cannabis use by adolescents may have long-lasting behavioral effects," said lead author Dr. Ken Mackie, professor in the IU College of Arts and Sciences' Department of Psychological and Brain Sciences and director of the Linda and Jack Gill Center for Biomolecular Science at IU Bloomington. "It also suggests that strains of cannabis with similar levels of CBD and THC would pose significantly less long-term risk due to CBD's protective effect against THC."

THC, or tetrahydrocannabinol, is the chemical in cannabis that causes the "high" experienced during its use. Cannabis with higher levels of THC possess lower levels of the protective CBD, and vice versa, due to a biological link between THC and CBD production in the plant. An analysis of cannabis seized by the U.S. Drug Enforcement Administration found that while THC levels rose 300 percent from 1995 to 2014, the levels of CBD have declined 60 percent.