A team of US researchers has identified an unexpected connection between recreational cannabis use and a reduced risk of cognitive decline.
Scientists at Upstate Medical University in Syracuse, New York examined a large dataset sourced from the CDC (Centres for Disease Control and Prevention).
Their findings pointed to a striking association: people who used cannabis for non-medical, primarily recreational purposes were 96 per cent less likely to experience subjective cognitive decline (SCD) compared with those who did not use cannabis at all.
People who used cannabis for medical purposes or for both medical and recreational reasons also showed lower odds of SCD, though those results did not reach statistical significance. The frequency with which participants used cannabis and the method by which they consumed it showed no significant links to SCD.
SCD is considered an important early indicator because prior research has found that people who experience it face twice the risk of developing dementia, a condition for which there is currently no cure or reliable prevention.
Lead researcher Professor Roger Wong described the results as unexpected, given that earlier studies had associated cannabis use with cognitive deterioration. He cautioned, however, that the study has limitations and captures data from only a single year.
He said the main takeaway is that cannabis might offer protection for cognitive health, but stressed that longitudinal studies are essential.
Wong added it was important to understand if non-medical cannabis use leads to better cognition or if individuals with better cognition are more likely to use non-medical cannabis.
Long-term research is crucial, said Wong, but that is currently hindered by cannabis remaining illegal at the federal level in the US.
The study drew data from 4,744 US adults aged 45 and older who took part in the 2021 Behavioural Risk Factor Surveillance System (BRFSS). SCD was self-reported as an increase in confusion or memory loss within the past year.
Researchers assessed the odds of SCD based on the reason for cannabis use, how often it was used, and the method of consumption, after accounting for a range of sociodemographic, health, and substance-use variables.
The research is distinguished by its focus on middle-aged and older adults and its detailed treatment of cannabis-use patterns, including whether use was medical or non-medical, how frequently it occurred, and how the substance was consumed.
Wong said he was surprised that mode and frequency had no bearing on SCD since other studies involving younger participants found a negative connection between brain health and cannabis use, perhaps suggesting that the age of the participants plays a role in the different results.
Although the study could not account for cannabis regulations that vary by state, it benefits from drawing on a national dataset. It also sheds light on the different protective effects of medical versus non-medical cannabis, attributed to the varying compositions of CBD and THC in each.
Wong theorised that the protective effect against SCD observed in non-medical users could stem from improved sleep and stress relief, common reasons for recreational use. Medical cannabis, by contrast, is more commonly used for pain management and did not show the same cognitive health benefits.
“Based on our findings, we don’t see the CBD in medical cannabis being beneficial for cognitive health,” he concluded.