Lifetime cannabis use is associated with several aspects of brain structure and function in later life but cannabis use may not be the cause of these changes, according to a new study by researchers at Oxford Population Health and the University of Oxford’s Department of Psychiatry.

Previous studies have not been able to pinpoint whether cannabis can cause neurocognitive decline or damage to the brain. It is also not currently known whether there is a safe threshold for cannabis use.

The study “Association between cannabis use and brain structure and function: an observational and Mendelian randomisation study”, published in BMJ Mental Health, was the largest observational study of relationships between cannabis use and brain structure and function to date and the first to use genetic data to determine whether cannabis causes brain changes.

Some key findings included that cannabis use was associated with multiple measures of changes in brain structure and function and participants who had ever used cannabis had poorer white matter integrity, a part of the brain that is important for cognitive function.

The research was supported by Oxford Health NHS Foundation Trust Honorary Consultant Psychiatrist Anya Topiwala and Professor of Old Age Psychiatry Klaus Ebmeier.

For more information, visit the Oxford Population Health webpage.