Thursday, August 13, 2015
International Centre for Science in Drug Policy releases "State of the Evidence: Cannabis Use and Regulation"
I am very pleased to see that the International Centre for Science in Drug Policy (ICSDP), a group of scientists and academics who seek to "ensure that policy responses to the many problems posed by illicit drugs are informed by the best available scientific evidence," has released this effective and timely new report titled "State of the Evidence: Cannabis Use and Regulation." Here is the report's introduction:
The regulation of recreational cannabis markets has become an increasingly important policy issue in a number of jurisdictions. Colorado and Washington State made headlines in 2012 when they became the first jurisdictions in the world to legalize and regulate the adult use and sale of cannabis for non-medical purposes. In 2013, Uruguay became the first country to legalize and regulate recreational cannabis markets. Momentum towards regulation continued in the United States in 2014 with successful ballot initiatives in Alaska, Oregon, and the District of Columbia. Globally, the issue of cannabis regulation is front and center in a growing number of jurisdictions, including Canada, Jamaica, Italy, Spain, several Latin American countries, and a number of additional U.S. states, including California, set to vote on legalization initiatives in 2016.
Unsurprisingly, given the robust global conversation around the regulation of recreational cannabis markets, claims about the impacts of cannabis use and regulation are increasingly part of the public discourse. Unfortunately, though, these claims are often unsupported by the available scientific evidence. Another reoccurring problem in the public discourse is the selective inclusion of research studies based on their support for a predetermined narrative. The intentional exclusion of studies with contradictory findings does not allow for an objective review and analysis of all the evidence. This “cherry picking” of the evidence is a routine practice that distorts public understanding. By outlining the current state of all the scientific evidence on common cannabis claims, State of the Evidence: Cannabis Use and Regulation strives to ensure that evidence, rather than rhetoric, plays a central role in policymaking around this important issue.
The harms of misrepresenting the scientific evidence on cannabis should not be overlooked. Given that policy decisions are influenced by public opinion and media reports, public discourse needs to be well informed. By addressing knowledge gaps with scientific findings, the ICSDP hopes to dispel myths about cannabis use and regulation, and ensure that the scientific evidence on these topics is accurately represented. Only then can evidence-based policy decisions be made.
Readers of this report will notice three repeating themes emerge through the discussion of the scientific evidence on common cannabis claims.
First, many of the claims confuse correlation and causation. Although scientific evidence may find associations between two events, this does not indicate that one necessarily caused the other. Put simply, correlation does not equal causation. This is a commonly made mistake when interpreting scientific evidence in all fields, and is unsurprisingly a recurring source of confusion in the discourse on cannabis use and regulation.
Second, for several of these claims, the inability to control for a range of variables (“confounders”) means that in many cases, we cannot conclude that a particular outcome was caused by cannabis use or regulation. Unless scientists can remove all other possible explanations, the evidence cannot conclusively say that one specific explanation is true.
Third, many of the claims cannot be made conclusively as there is insufficient evidence to support them. Findings from a single study or a small sample cannot be generalized to entire populations. This is especially pronounced for claims related to cannabis regulation, as not enough time has passed since the regulation of recreational cannabis in Colorado, Washington State, and Uruguay to examine many of the impacts of these policy changes.
These three common pitfalls are important to take into account when reading media reports and advocacy materials that suggest scientists have conclusively made some finding related to cannabis use or regulation. In many cases, due to the reasons outlined above, this will actually result in a misrepresentation of the scientific evidence.
State of the Evidence: Cannabis Use and Regulation is comprised of two sections: Common Claims on Cannabis Use and Common Claims on Cannabis Regulation.
Common Claims on Cannabis Use presents evidence on frequently heard claims about cannabis use, including claims on the addictive potential of cannabis, cannabis as a “gateway” drug, the potency of cannabis, and the impact of cannabis use on the lungs, heart, and brain (in terms of IQ, cognitive functioning, and risk of schizophrenia).
Common Claims on Cannabis Regulation presents evidence on frequently heard claims about the impacts of cannabis regulation, including the impact of regulation on cannabis availability, impaired driving, the use of cannabis, drug crime, drug tourism, and “Big Marijuana.”
For each claim, the relevant available scientific evidence is presented and the strength of the scientific evidence in support of the claim is determined. Readers will notice that none of the claims are strongly supported by the scientific evidence, reinforcing the significant misrepresentation of evidence on cannabis use and regulation.
We hope that the evidence contained in this report meaningfully contributes to the global conversation around cannabis policy and helps policymakers, as well as general readers, separate scientific evidence from conjecture.