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Dear Editor
I read with interest the study “Open Access: The effect of legislation on firearm-related deaths in Canada: a systematic review”, submitted by Bennet et. al.
While it was an interesting summary and a careful search, I believe it would have benefitted from a more in-depth review. I will offer some comments below and suggest some changes, as well as some errors. I hope this critique will help the authors of this paper.
In the introduction it is important to note that even though legislation was passed on certain dates, regulations were not implemented until some time after those dates. For instance regarding C68 it is very important to note that licensing was not actually implemented until 2001, and the long gun registry was not fully implemented until 2003 with most firearms registered in 2002 according to the Auditor General. This is important information because examining time series studies requires ensuring that proper cut offs are chosen for breakpoints.
The article would have benefitted from a much more in-depth discussion of the quality of studies, in particular regarding homicide. The earlier studies by Leenaars and Lester, among others, use a simple form of analysis where examination of average rates pre and post legislation are examined. As well trends pre and post are also examined but not assessed for statistical significance. This type of analysis, while available at the time, would never pass statistical review today wi...
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As well a deeper delve into the study methods would have been beneficial. The Blais et al. 2011 paper only examines the effects of legislation up until 2004. Which means that licensing is not examined at all since one cannot make inferences about this regulation from 3 years of data as licensing was not fully implemented until 2001. It cannot make any claims about licensing. Studies that examined longer time frames such as Langmann 2012 and Langmann 2020 examined longer time periods. A discussion of this would have improved the review.
Time series linear regression studies require the examination of an impact and trend effect. The Blais et al 2011 study only examines impacts and does not look at trends, leaving it prone to erroneous findings as an increasing trend after legislation can produce an increasing trend with what appears to be a sudden lower impact however resulting in overall higher rates of homicide in later years past the intervention. This error leads one to believe there is a benefit when in fact there is a worsening of homicide rates.
The Blais et al 2011 study and the Bridges 2004 study do not use all available independent variables. Blais mentions under a table that they leave out many variables due to collinearity. This is an important discussion point and should have been fleshed out in the review as for time series analysis it is important to include other independent variables that may account for the effect other than just legislation...
Show MoreCompeting Interests: None declared.References
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This research has been conducted using the CLSA Baseline Comprehensive Dataset version 4.1 and follow-up 1 Comprehensive Dataset version 3.0 under Application Number 1909010.
Competing Interests: None declared.References
- Bennett N, Karkada M, Erdogan M, Green RS. The effect of legislation on firearm-related deaths in Canada: a systematic review. Apr 2022, 10 (2) E500-E507