The results of the mediation analysis did not support the hypothesis that changes in perceptions of the proportion of people who used cannabis between baseline and three-months were positively associated with reduction in the participant’s risky cannabis use at six-month follow-up . The analyses also did not demonstrate any evidence that these changes in perceptions mediated the effect of the intervention on risky cannabis use at six-month follow-up, indirect effect estimate = 0.06, 95% CI [− 0.08, 0.22]. In the current era of rapidly shifting cannabis policies, there is a need for accessible and scalable interventions for individuals who are engaging in risky cannabis use. This study examined the efficacy of a brief, online personalized normative feedback intervention in a large, non-college sample of adults in Canada following national legalization of recreational cannabis use. Participants who received the personalized normative feedback intervention did not reduce their cannabis use between baseline and three- and six-month follow-ups to a greater extent than those who received the educational materials only. Further, while receiving the normative feedback information did have an impact of participants’ perceptions of how common cannabis use was among adults of the same age and gender, this change did not mediate the impact of the intervention on their own cannabis risk level. As such, it appears that the trial failed to find a significant impact of the intervention on cannabis use. There are several possible reasons for these findings. One possibility is that the educational materials also motivated reductions in cannabis use and the intervention was unable to promote a larger reduction than the provision of these materials alone.
However, the current trial was not designed to test for this possibility so it would be inappropriate to claim that both interventions worked. Another possibility is that the intervention was not an effective means of motivating reductions in cannabis use,particularly among our sample of somewhat heavier users of grow cannabis. As brief interventions are meant for those with ASSIST scores over 4, and not necessarily on the end of the scale, this may have contributed to the findings observed. Moreover, a recent meta-analysis uncovered that personalized normative feedback may not be effective at reducing drug use without the provision of additional interventions . While the literature is still quite young on the use of personalized normative feedback for substances other than alcohol, we cannot assume the intervention was completely ineffective. The intervention was developed based on a sound theoretical foundation andemployed content that has demonstrated efficacy in motivating change in trials targeting other addictive behaviors. This does raise the interesting possibility that there is something different in the use of cannabis versus the consumption of alcohol that then makes social comparisons, and the correction of normative misperceptions, ineffective as a means to motivate change. Perhaps, while the recreational use of cannabis is now legal in Canada, there is still a counter-cultural mystique to its use. Also related, some participants provided feedback that cannabis use was healthy and queried why we were trying to say its use was bad. While these comments were not common, they might capture the general tone of a proportion of those people recruited for the trial – i.e., being unconcerned about their own cannabis use but instead participating because they were interested in issues relating to using cannabis . Other relevant factors to consider when interpreting the results of this trial have to do with the time when it was conducted. First, cannabis use was legalized just a few years previously and the ready availability of cannabis from commercial sources was still continuing to expand . This relative newness of cannabis as a legal substance might be a situation where normative comparisons are less meaningful to those receiving them. Further, with the prevalence of cannabis use increasing, it might be easier for participants to discount information about how much others smoke .
Finally, it is unknown what the impact of the pandemic had on peoples’ need to find activities that were distracting or on the efficacy of this intervention. There were several limitations associated with the trial. First, while we incorporated extensive checks to prevent multiple registrations by one person, we relied on self-report regarding cannabis use both at the time of recruitment and at follow-up. Second, the outcome measures employed were fairly crude. Perhaps, in an environment where cannabis is legal, the variable number of days used cannabis in the past 30 might suffer from a ceiling effect if a substantial proportion of participants are using cannabis every day. Finally, while the trial was powered to detect a small effect, it is certainly possible that the intervention, if effective, would only ever have an impact that is very small; especially among heavy users of cannabis. Given that this is a low-cost intervention that can be distributed widely, having a very small impact is not necessarily a rule-out of the intervention’s utility. It just implies that a much larger sample would be needed to establish efficacy, perhaps across a wider range of cannabis users. The prevalence of cannabis use world-wide has been fairly stable over the past decade, with an estimated 3.8 per cent of the global population aged 15–64 in 2018 having used cannabis at least once in the previous year, compared to 3.6% in 2008 . Cannabis use in the United States has been increasing since 2002, adding an average of 7,000 new users daily. In 2014, 8.4% of the population were current cannabis users , representing an increase of 35% over 2002 rates . Cannabis use has increased across adult age groups , with 18–25 year-olds having the highest current-use rate , of whom a large portion reported daily or almost daily cannabis use . Usage rates by country are reported by the United Nations in Table 1.1.1 of their World Drug Report .Combustion of tobacco and cannabis is common and produces heavy particulate matter emissions , which is a significant agent of cardiovascular harm . Furthermore, the chemical composition of cannabis smoke is similar to that of tobacco smoke with the two having similar levels of cytotoxic, mutagenic, and carcinogenic substances Cannabis smoke contains higher levels of ammonia, hydrogen cyanide, 1,3-butadiene, and acrylonitrile—constituents identified as harmful or potentially harmful by the FDA .
The Global Adult Tobacco Survey found that of approximately one billion children under age 15 in 21 countries, 51% were exposed to SHS . However, efforts to restrict tobacco smoking are encouraging and lead to lower SHS exposure. As of 2017, more than 30 countries globally had instituted at the highest level at least 4 of the 6 most important tobacco control policies that were first recommended in 2008 by the World Health Organization . At least one MPOWER tobacco control policy measure is in effect for approximately 65% of the world population . Details of tobacco smoking regulations by country are provided by the World Health Organization in Tables 6.1, 6.2, and 6.3 of their report on the global tobacco epidemic . The 3 tables reveal considerable variation in smoke-free legislation by country regarding the sorts of locations or establishments restricted, kinds of restrictions imposed, level of compliance, investigations of complaints, consequences for violations, etc.; there are also regulations that vary by region in some countries. Level of regulation likely influences home smoking rules and behaviors.Fortunately, tobacco control efforts have successfully reduced the number of people who smoke tobacco in their home. In Spain, assessments conducted before implementation of two national smoking bans in public and work places and 9 years later showed an increase in voluntary adoption of smoke-free home rules . England saw a trend to more smoke-free homes from 1996 to 2007, with a concomitant decrease in SHS exposure . In the U.S., the national prevalence of smoke-free home rules increased from 43.0% to 86.8% between the 1992–1993 and 2014–2015 surveys , while SHS exposure prevalence among nonsmokers declined from 52.5% to 25.3%. In California, the proportion of smokers exposed to in-home cigarette smoke decreased from 24.0% in 2003 to 13.0% in 2011, while a similar relative decrease was observed among nonsmokers In parallel with tobacco regulations, cannabis control policies appear to impact cannabis use. In its Global Drug Report 2020, the United Nations noted that in jurisdictions that have legalized cannabis use, frequency of cannabis use has subsequently increased . Analysis of data for a US representative sample of adults with children living in the home found cannabis use to be more common in states that had legalized recreational cannabis use , possibly leading to increased in home cannabis smoking and concomitant exposure of non-smokers.
An overview of recreational cannabis use regulation by country is presented by Wikipedia on their “Legality of cannabis” web page . The data demonstrate a substantial diversity across countries regarding whether cannabis has been legalized or decriminalized, the venues restricted, level of enforcement, and consequences for violations. In the US, a growing number of states have legalized cannabis for recreational or medicinal purposes, adding another layer of complexity. As with smoke-free ordinances for tobacco use, the level of constraint imposed by cannabis control policies is likely to affect home smoking rules and behaviors. While information about rates of in-home cannabis smoking and in home exposure to cannabis SHS are not yet available, there is evidence that the perception of health risks associated with cannabis smoke is lower than for tobacco smoke . Furthermore, early evidence from US studies of household rules about in-home smoking suggests that 59% to 71% of people who used cannabis allow cannabis smoking inside their home, while just 26% allowed tobacco smoking in their home . With lower rates of in-home tobacco smoking, lower perceived risk of cannabis smoke, and relatively lax household rules surrounding in-home cannabis smoking, we expect higher rates of in-home cannabis smoking than in home tobacco smoking. To test this hypothesis, we used data from over 100,000 adults from 17 countries to compare in-home cannabis and tobacco smoking among 2019 Global Drug Survey respondents who use cannabis only, tobacco only, both tobacco and cannabis, or neither。Data for this cross-sectional analysis were from the 2019 GDS survey. The GDS is the world’s largest anonymous self-administered internet based drug survey. It was designed by substance use experts to assess existing and nascent patterns of substance use worldwide among annual samples of sentinel, more involved drug-using populations . The GDS promotes their survey via media partners from around the world such as HUFFPOST, VICE, MixMag, Fairfax Media, and The Guardian. They also use targeted social media campaigns on Facebook, Twitter, Reddit and drug discussion forums. The 2019 survey was available in 19 languages and collected data from over 35 countries. The core survey assessed demographics, drug use and consequences and in 2019 took about 15–20 min to complete—additional sections on psychedelic therapies, indoor cannabis grow system edibles, and sex and drugs took an additional 25 to 30 min. No financial incentive was provided. Participants confirmed they were ≥ 16 years old, but there were no other eligibility requirements; participation was open to individuals regardless of participation in any prior year administration of the annual GDS.
For the current study, eligible participants included 123,814 persons who took the GDS between October 29, 2018 and January 10, 2019 and reported past-year use of at least one of 31 psychoactive drugs, including the most commonly used: tobacco, alcohol or cannabis. Consistent with previous GDS analyses, only countries that had greater than 1,500 respondents were included so that country-specific analyses could be conducted—therefore data from 17 countries were used, excluding 14,178 participants. Participants were also excluded if they were missing data on cannabis use, tobacco use, or in-home smoking of cannabis or tobacco . The remaining 107,274 comprised our final analytic sample. Ethical approval was obtained from the separate institutions: Joint South London and Maudsley and Institute of Psychiatry NHS , the University of Queensland and The University of New South Wales . See Barratt et al. for more information on the methods of the GDS. Participant characteristics were summarized for the total sample and stratified by the four tobacco and cannabis use groups.