High-potency cannabis damages key brain structure

by Honor Whiteman

Researchers have previously linked the use of high-potency, "skunk-like" cannabis to increased risk for psychosis - an effect that has been attributed to alterations in brain structure. Now, a new study finds frequent use of the drug damages a key part of the brain that aids communication between the right and left hemispheres, independent of psychosis.

Researchers found the use of high-potency cannabis damaged the corpus callosum of the brain - a structure that aids communication between the right and left hemispheres.

 

Senior researcher Dr. Paola Dazzan, of the Institute of Psychiatry, Psychology & Neuroscience at King's College London in the UK, and colleagues publish their findings in the journal Psychological Science.

In the US, cannabis is the most commonly used illicit drug. Skunk is a more potent form of cannabis, typically stronger in smell and containing higher levels of the main active ingredient delta-9-tetrahydrocannabinol (THC).

Studies have increasingly associated the use of skunk cannabis with increased risk of psychosis - a term used to describe hallucinations and delusions that arise from some mental disorders, such as schizophrenia. Another study by King's College published earlier this year, for example, linked high-potency skunk use to a fivefold greater psychosis risk.

For this latest study, Dr. Dazzan and colleagues investigated how the high-potency drug affects brain structure. They note that gaining a better understanding of this association is important, particularly since levels of THC in skunk-like cannabis have been increasing in recent years, and this ingredient itself has been linked to increased psychosis risk.

Heavy users of high-potency cannabis showed greatest brain damage

To reach their findings, the team enrolled 54 individuals with first-episode psychosis and 43 healthy participants. Using the Cannabis Experience Questionnaire, information was gathered on subjects' past use of cannabis, stimulants and other recreational drugs.

Each participant underwent a magnetic resonance imaging (MRI) technique known as diffusion tensor imaging (DTI), which allowed the researchers to closely analyze their brain structure.

Specifically, the team assessed the corpus callosum - a white matter structure that connects the right and left hemispheres of the brain, allowing communication between the two. The team notes that this brain region has lots of cannabinoid receptors, which THC targets.

The researchers found that participants who had a history of frequent high-potency skunk use demonstrated much higher mean-diffusivity (MD) in the corpus callosum - a marker of white matter damage - than low-potency users and those who used the drug occasionally. What is more, this association was found in subjects both with and without psychosis.

Commenting on the results, Dr. Dazzan says:

"We found that frequent use of high-potency cannabis significantly affects the structure of white matter fibers in the brain, whether you have psychosis or not. This reflects a sliding scale where the more cannabis you smoke and the higher the potency, the worse the damage will be."

Based on the findings of this study and others showing how cannabis may damage the brain, Dr. Dazzan says there is an "urgent need" to educate health professionals, policymakers and the general public about the health risks that may arise with cannabis use.