BLOOMINGTON, Indiana- Neuroscientists at Indiana University finds in their study that a non-psychoactive compound in cannabis called cannabidiol, or CBD, may protect against the long-term negative psychiatric effects of THC, which is the primary psychoactive ingredient in cannabis.
Long-term use of cannabis ups adolescent drug users' risk for certain psychiatric and neurological disorders, such as schizophrenia. There’s greater risks to teens since selective breeding of plants produce higher levels of THC over the past several decades has substantially increased.
“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 induce the feeling of “high” during its use. Cannabis has lower levels of the protective CBD compared to THC that is due to a biological link between THC and CBD production in the plant. THC levels rose 300 percent from 1995 to 2014 while the levels of CBD have declined 60 percent, according to U.S. Drug Enforcement Administration cannabis analysis .
On the other hand, CBD oil does not cause a “high.” It is also an important ingredient in medical cannabis. For instance, CBD appears useful as a treatment for some forms of severe childhood epilepsy. Its use for severe epilepsy was approved by the Indiana legislature this year.
“This is the first study in a rigorously controlled animal model to find that CBD appears to protect the brain against the negative effects of chronic THC,” Mackie said. “This is especially important since heavy use of cannabis with higher levels of THC poses a serious risk to adolescents.”
IU researchers divided adolescent or adult male mice into five groups to begin their study. Three groups acquired 3 mg per kilogram of body weight of either THC, CBD, or THC with CBD every day for three weeks. Meanwhile, the two other groups received a placebo or no treatment.
All mice were then tested for signs of impaired memory, obsessive-compulsive behaviors. It was followed by six weeks of treatment.
Mice exposed to THC alone showed signs of impaired memory and increased obsessive-compulsive behavior immediately after treatment. The adolescent group still experienced these changes six weeks after treatment. However, the adult group did not. Both groups experienced a long-term anxiety increase.
Adult and adolescent mice, which are given CBD alone, showed no behavioral changes immediately or six weeks after treatment. Both age groups that received CBD with THC showed no short- or long-term behavioral changes. These results suggest that long-term use of cannabis strains containing similar amounts of CBD and THC may be less harmful than long-term use of high-THC strains.