Since legalization for nonmedical purposes starting in 2018, the prevalence of cannabis use has been increasing in Canada. ^{Reference Canada1} This increase in use is the greatest in people over the age of 50. ^{Reference Imtiaz2} About 10% of people who use cannabis do so for medical purposes, and only 18% of people who use cannabis for medical purposes have an authorization from a physician. ^{Reference Canada1} Cannabis can be effective in treating various illnesses, including some forms of pain, chemotherapy-induced nausea, the spasticity associated with multiple sclerosis and some types of epilepsy in children. ³ In addition, there have been clinical trials investigating the efficacy of cannabis in treating a number of illnesses, including anxiety and insomnia. ^{Reference Narayan, Downey, Manning and Hayley4} Most relevant to the present discussion, some studies have shown the efficacy of cannabis in treating the aggression and agitation associated with dementia. ^{Reference Sawicki, Hernandez, Laiteerapong and Zahradnik5}

The paper by Yao et al. addresses a gap by studying older adults who use cannabis and are seeking the support of a memory clinic. It looked at differences between cannabis users and nonusers on measures of age, sex, race, education level, smoking status, frequency of alcohol use, cognitive diagnosis, cannabis use characteristics, medical history including psychiatric history, agitation and scores on the Montreal Cognitive Assessment and Mini-Mental State Examination. Cannabis users were younger, more likely to be present or past smokers and more likely to report mood disorders. All other outcomes were the same, and most notable is that cognitive function and agitation (related to dementia) were the same in both groups.

Observational studies afford a great deal of external validity. Being free of the strict constraints of clinical trials, they provide an insight into the real-world use of cannabis. However, this succinct data set with a small sample of cannabis users (n = 23) leaves unanswered a number of questions. First, the scores on agitation did not vary between groups, which is where cannabis is believed to have effects in dementia. Future studies will need a comprehensive evaluation of these symptoms in larger samples. Also, there is variability in the delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) content in the products used; THC and CBD have differential therapeutic effects. Further, only a small sample used cannabis for medical purposes, and it is not clear what those indications were. Demographics, with a larger data set, could also be better characterized to get some insights into the impact of cannabis on subsamples.