Key points from article :
A new study from Oxford Population Health and the Department of Psychiatry, published in BMJ Mental Health, examines how lifetime cannabis use relates to brain structure and function. This large-scale study, the first of its kind to use genetic data to assess causation, suggests that while brain changes are associated with cannabis use, it may not necessarily cause these changes. The study adds an important dimension to understanding cannabis's effects, as its use has grown globally due to legalisation for both medical and recreational purposes.
Using data from 15,896 UK Biobank participants, researchers assessed MRI scans and found notable differences in brain structure between cannabis users and non-users. In particular, cannabis users showed reduced white matter integrity—a crucial factor for cognitive function—and differences in brain connectivity. Interestingly, men and women displayed these associations differently, with men showing changes primarily in brain connectivity, and women in white matter integrity.
However, genetic analyses found no evidence supporting a causal link between cannabis use and neurocognitive decline or brain structure changes. Dr. Anya Topiwala, a Senior Clinical Researcher, highlighted that other unmeasured variables, like diet or medication use, might explain the observed associations in the observational data. The study also notes limitations, such as the predominantly healthy, White participant group and the challenges in accurately recalling lifetime cannabis use.
While the findings show associations between cannabis use and brain changes, they caution that further research is needed to fully understand the effects of long-term and heavy cannabis use, including differences in potency and factors influencing susceptibility. This research underlines the importance of cautious interpretation, particularly as cannabis becomes more accessible worldwide.
