For the first time ever, scientists are examining the effects of cannabis on brain structure - specifically, the effects of "skunk-like" cannabis on the corpus callosum, the part of the brain responsible for the communication between the two hemispheres. "Skunk cannabis" refers to high-potency products that possess increased levels of Δ9-tetrahydrocannabinol (THC).

Recent research points to a connection between long-term cannabis use and psychosis, and now, scientists at King's College London have found that the frequent use of "skunk-like" cannabis affects the structure of the brain's white matter fibers, in particular those in the corpus callosum.

"We found that frequent use of high potency cannabis significantly affects the structure of white matter fibres in the brain, whether you have psychosis or not," Paola Dazzan, senior researcher of the study, said in a press release. "This reflects a sliding scale where the more cannabis you smoke and the higher the potency, the worse the damage will be."

The study used Diffusion Tensor Imaging (DTI), a Magnetic Resonance Imaging (MRI) technique that allowed the researchers to examine the white matter in the brains of 56 patients, all of whom reported their first psychotic episode at the South London and Maudsley NHS Foundation Trust (SLaM). This data was then compared to data gathered from 43 healthy subjects from the surrounding community.

"White matter damage was significantly greater among heavy users of high potency cannabis than in occasional or low potency users, and was also independent of the presence of a psychotic disorder," said Tiago Reis Marques, co-author of the study.

The findings are worrying due to the fact that "skunk-like" products are the most common forms of cannabis used in the U.K., leading experts to fear for long-term damages that users could do to their brains.

"As we have suggested previously, when assessing cannabis use it is extremely important to gather information on how often and what type of cannabis is being used," said Dazzan. "These details can help quantify the risk of mental health problems and increase awareness on the type of damage these substances can do to the brain."

The study was published in the Nov. 26 issue of the journal Psychological Medicine.