Researchers have used functional magnetic resonance imaging (fMRI) to show how cannabidiol (CBD) counteracts some of the harmful effects of cannabis on the brain
The team performed fMRI on 17 healthy volunteers after taking strains of cannabis containing tetrahydrocannabinol (THC), the main psychoactive component in cannabis, and either high CBD or negligible CBD.
They found that the low-CBD strain resulted in disruption in certain areas of the brain involved in processing sensory and emotional inputs. However, the high-CBD strain had minimal effects on these regions, suggesting that CBD counteracts some of THC’s harmful effects.
Writing in the Journal of Psychopharmacology (23 April 2019), the researchers said their findings support the idea that THC is responsible for harmful effects in cannabis users because the brain areas in the study are linked with addiction and psychosis. CBD, which is virtually absent in strong cannabis varieties such as ‘skunk’, appears to counteract them.
Lead author Matthew Wall, a researcher in the clinical psychopharmacology unit at University College London, said: “As cannabis is becoming legal in more parts of the world, people buying cannabis should be able to make an informed decision about their choice of cannabis strain and be aware of the relative risks.”
 Wall MB, Pope R, Freeman TP et al. Dissociable effects of cannabis with and without cannabidiol on the human brain’s resting-state functional connectivity. J Psychopharmacol 2019. doi: 10.1177/0269881119841568