A first-of-its-kind study of the effects of high-potency marijuana on brain structure shows it can damage the corpus callosum (imaged above), a huge section of white matter that consists of nerve fibres responsible for communicating between the two halves of the brain. This part of the brain is rich in receptors to which THC binds. Study results “reflect a sliding scale where the more cannabis you smoke and the higher the potency, the worse the damage will be,” says Dr. Paoloa Dazzan, reader in neurobiology of psychosis at the institute of psychiatry, psychology, and neuroscience at King’s College London and senior researcher of the study. Scientists recruited 56 people reporting a first-episode psychosis and 43 people without psychosis and administered clinical and brain imaging assessments to all. The structure of the white matter of high-potency marijuana users in both groups – those with and those without psychosis – was significantly damaged. High-potency marijuana they used contained from 16-22% THC and 0.1% CBD. The Brits call this “high-potency” and “skunk,” while U.S. marijuana dispensaries and pot shops in legal states call this average. Here, marijuana concentrates such as wax or shatter contain much higher levels of THC, from 50-75%. The researchers note that their study cannot confirm that THC caused the structural changes – it may be that people with damaged white matter are more likely to smoke marijuana. But what they can say is that if you smoke marijuana frequently and it is high-potency, your brain is different from the brains of those who use low-potency marijuana infrequently or not at all.

ScienceDaily 27th November 2015