Cannabis Not Linked to Brain Aging
A new study in the British Medical Journal finds no evidence that cannabis causes dementia or accelerates brain aging in older adults. Genetic tests reportedly confirmed no causal link between cannabis use and cognitive decline, and the research even noted potential benefits for some patients.
The new research, published in *BMJ Mental Health*, analyzed data from two extensive long-term studies: the UK Biobank and the US Million Veteran Program, encompassing hundreds of thousands of participants. Researchers from Oxford Population Health and the University of Oxford's Department of Psychiatry led the large-scale observational study. The study compared cognitive performance across five different domains—including numeric memory, pair matching, and problem-solving—between cannabis users and non-users. It found no evidence that cannabis use was associated with an increased risk of dementia or accelerated cognitive decline in older adults. In fact, at the study's baseline, individuals with a history of cannabis use demonstrated slightly better performance on some cognitive tests. However, the authors suggest this improved performance is likely due to confounding variables rather than a direct neuroprotective effect of cannabis. In the UK Biobank cohort, cannabis users tended to have a higher socioeconomic background and more education than non-users, which could explain the better cognitive scores. The genetic analyses performed as part of the study supported this conclusion, finding no evidence of a causal link. This study aligns with other recent research challenging long-held beliefs about cannabis and cognitive aging. For instance, a Danish study of over 5,000 men found no significant harmful effects of cannabis use on age-related cognitive decline. Similarly, an Israeli study involving over 67,000 older adults reported that participants with a history of cannabis use performed better across several cognitive domains. Researchers caution that these findings do not mean cannabis is entirely without risk. The study's authors noted limitations, such as the UK Biobank participants being generally healthier than the wider population and the inability to measure the potency of the cannabis used. Therefore, they emphasize that further research is needed to understand the effects of long-term, high-dose cannabis use on brain health in later life.
