Many people will tell you that marijuana is less harmful than alcohol, but a recent study calls this assertion into question. According to a report from Medical News Today, a recent study published in the journal Psychological Science suggests that smoking high-potency marijuana is linked to a significant change in a key brain structure.
The study, led by senior researcher Dr. Paola Dazzan from the Institute of Psychiatry, Psychology Neuroscience at King’s College in London, showed that heavy users of cannabis with a high concentration of THC, the main psychoactive ingredient in marijuana, were the most likely to show evidence of brain damage.
The study examined 54 individuals who had experienced at least one episode of psychosis, as well as 43 individuals who were given a clean bill of health. The two groups provided information to the researchers about their drug use history by filling out the Cannabis Experience Questionnaire. In addition to asking about their history of cannabis use, the survey also asked about stimulants and other recreational substances.
The participants were given MRI scans using a technique called diffusion tensor imaging. This allowed researchers to get a detailed view of the brain structures in each of the participants.
The team was particularly interested in a region of the brain called the corpus callosum. Made primarily of white matter, the structure connects the right and left hemispheres in the brain, providing connectivity between the creative and mechanical sides.
The study found that participants who historically used high-potency cannabis on a frequent basis were more likely to have a higher mean-diffusivity in the corpus callosum. This measure is a marker of white matter damage, and there was a strong correlation between heavy cannabis users and high mean-diffusivity in the corpus callosum.
The study suggests that marijuana is not as harmless as many people believe. Heavy and frequent users of high-potency cannabis run the risk of damaging the white matter fibers in the corpus callosum, which could lead to a large number of cognitive issues down the line.
A press release from King’s College outlining the details of the study can be found here.
“Smoking high potency ‘skunk-like’ cannabis can damage a crucial part of the brain responsible for communication between the two brain hemispheres, according to a new study by scientists from King’s College London and Sapienza University of Rome.
Researchers have known for some time that long-term cannabis use increases the risk of psychosis, and recent evidence suggests that alterations in brain function and structure may be responsible for this greater vulnerability. However, this new research, published today inPsychological Medicine, is the first to examine the effect of cannabis potency on brain structure.
Exploring the impact of cannabis potency is particularly important since today’s high potency ‘skunk-like’products have been shown to contain higher proportions of Δ9-tetrahydrocannabinol (THC) than they did around a decade ago. In experimental studies THC has been shown to induce psychotic symptoms and ‘skunk-like’ products high in THC are now thought to be the most commonly used form of cannabis in the UK.
Dr Paola Dazzan, Reader in Neurobiology of Psychosis from the Institute of Psychiatry, Psychology Neuroscience (IoPPN) at King’s College London, and senior researcher on the study, said: ‘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.
‘This reflects a sliding scale where the more cannabis you smoke and the higher the potency, the worse the damage will be.’
Diffusion Tensor Imaging (DTI), a Magnetic Resonance Imaging (MRI) technique, was used to examine white matter in the brains of 56 patients who had reported a first episode of psychosis at the South London and Maudsley NHS Foundation Trust (SLaM), as well as 43 healthy participants from the local community.
The researchers specifically examined the corpus callosum, the largest white matter structure in the brain, which is responsible for communication between the left and right hemispheres. White matter consists of large bundles of nerve cell projections (called axons), which connect different regions of the brain, enabling communication between them.
The corpus callosum is particularly rich in cannabinoid receptors, on which the THC content of cannabis acts.
The study found that frequent use of high potency cannabis was linked to significantly higher mean-diffusivity (MD), a marker of damage in white matter structure.
Dr Tiago Reis Marques, a senior research fellow from the IoPPN at King’s College London, said: ‘This 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.’
Dr Dazzan added: ‘There is an urgent need to educate health professionals, the public and policymakers about the risks involved with cannabis use.
‘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. 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.’”