Recreational cannabis use may protect against cognitive decline – study

A new study has linked the consumption of cannabis for recreational purposes to a reduced risk of cognitive decline.

Researchers at Upstate Medical University have found that compared to non-users, non-medical cannabis use, such as for recreational purposes, was significantly associated with 96% decreased odds of subjective cognitive decline (SCD). 

SCD is an important outcome of interest as prior research shows individuals with SCD have a two times higher risk for dementia, which currently has no cure or definitive prevention approaches.

Medical and dual (medical and non-medical) use were also associated with decreased odds of SCD, although not significant. Cannabis consumption frequency and method were also not significantly associated with SCD.

For the study, Master of Public Health (MPH) student Zhi Chen and Professor Roger Wong, PhD, MPH, MSW, analysed data from the Centers for Disease Control and Prevention (CDC) on 4,744 US adults aged 45 and older in the 2021 Behavioral Risk Factor Surveillance System (BRFSS).

SCD was a self-reported increase in confusion or memory loss in the past year. 

Odds of SCD by cannabis use reason, frequency, and method were examined after imputing missing data, applying sampling weights, and adjusting for sociodemographic, health, and substance use factors.

The study differs from previous research in that it focuses on middle-aged and older adults, and it uniquely considers the three facets of cannabis use: type of use (medical or non-medical), frequency of use, and mode of use (smoking, vaping, eating or dabbing).

READ MORE: Alzheimer’s and medical cannabis: a new hope for patients?

Professor Wong said the results were surprising, though he pointed out several limitations of the study and the need for further research. 

“The main takeaway is that cannabis might be protective for our cognition, but it is really crucial to have longitudinal studies because this is just a snapshot of 2021,” said Wong, assistant professor in the Department of Public Health & Preventive Medicine. 

“We do not know if non-medical cannabis leads to better cognition or the other way around if those with better cognition are more likely to use non-medical cannabis. 

“We need longitudinal studies to see long term if non-medical cannabis use is protecting our cognition over time. That’s something we don’t know yet, but that research is hindered since cannabis remains illegal federally.”

He added: “The reason I think this study is so great is we looked at all the different dimensions of cannabis use. The fact that we included all three is a huge contribution to the research because I do not believe such a study has been done before.”

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, indicating perhaps that the age of the participants plays a role in the different results.

The authors did note some limitations with the study, including the inability to consider state-by-state cannabis regulations. Potential selection bias could arise if the population of certain states is either over or underrepresented due to varying measures of cannabis use. But the fact that the study includes a national data set, increases the generalisability of the findings. 

Wong said the difference in protection between medical and non-medical use comes down to the compounds that make up cannabis. Medical-grade cannabis often contains higher concentrations of CBD and lower levels of THC, compared to cannabis which is grown for recreational use.

Non-medical users often use cannabis to improve sleep and reduce stress. Poor sleep and chronic stress increase the risk for dementia, leading the authors to suggest that the protection in SCD could come from better sleep and stress relief that cannabis provides.

“Based on our findings, we don’t see the CBD in medical cannabis being beneficial for cognitive health,” Prof Wong added.

The full study is published in the journal Current Alzheimer Research.