To the Editor:

In last week’s Town Topics, a group of letter writers argued that town Council should use “current scientific data that proves there are too many dangers and unknowns to opt-in” to cannabis dispensaries [“Opting Out of Cannabis Dispensaries is Not Prohibition,” Mailbox, March 2]. But in their letter they misrepresent the data they cite.

Specifically, they write that a January 2021 study by the NIH found that “recreational marijuana legalization and greater retail availability of recreational marijuana and alcohol were positively associated with alcohol and marijuana co-use among adolescents.”

Firstly, to clarify, the study, published in the journal Substance Use and Abuse, was funded by the NIH but not conducted by the NIH. It was also specific to one state and one age group, using data from Oregon in 2010-2015 (before legalization) compared with 2016-2018 (post legalization).

What was found? The researchers state, “There was an overall downward trend in the prevalence of past-30-day alcohol and marijuana co-use from 2010 to 2018.” In one of their regression models they found a small increase (1 percent) in past 30-day alcohol and marijuana co-use in areas with high outlet density. This was only true in 2016, not 2018 — suggesting a temporary increase.

Second, the authors explicitly limit their findings. They state: “It is important to note that the nonexperimental and cross-sectional study design precludes causal interpretations of the findings” and they note that the analysis was based at the county and not at the city level. Interestingly, the same authors, in January 2022, published a study (also funded by NIH) looking at the same issues in California. They also found a slight decline in co-use of alcohol and marijuana after marijuana legalization.

This brings me to my broader point. In discussing cannabis dispensaries, we should avoid cherry-picking studies and suggesting individual studies can “prove” one’s point. There are complex considerations in weighing the strength of evidence and in the degree to which research results are generalizable to new locations, populations, and times.

Joe Amon
Ewing Street