Several social behavioral theories have placed perceived risks as a precursor to risky behavior,with lower risk perceptions leading to increased substance use.For example, young people who perceive long-term tobacco use as low risk are nearly four times more likely to start smoking than peers with high risk perceptions.Perception of harm for marijuana use has been decreasing in the United States, even among young people .The proportion of high school seniors reporting that regular marijuana use poses little to no health risks more than doubled between 2004 and 2014, from 20% to 45%.468 Youth at low risk for drug use report greater intentions to use marijuana if full legalization of medical and/or retail marijuana occurred.469 Data from Colorado show that risk perceptions among 18-25 year olds decreased from 2006 to 2014, with 18.5% of young adults perceiving “great risk” from once-per-month marijuana used in 2006 to 8.4% in 2014; among 26 years and above from 32.8% in 2006 to 19.8% in 2014 . 406 While use among youth has not increased since legalization of recreational use in 2013, perception of “great risk” from monthly marijuana use declined from 30% in 2006 to 17% in 2014, and past 30-day use was 12.6%, well above the national average of 7.2% . By 2014, almost 100% of the 10th and 12th grade current users reported no perceived harm. The 10th grade students reported no risk at 95%, 8th grade students reported no risk at 90%, and 6th graders reported no risk at 75%.407 Given the association between reduced risk perceptions and substance use, it is likely that as social norms on marijuana use increase and access becomes more widespread,hydroponic table use among youth will also increase in Colorado and Washington. US youth perceive marijuana to be either harmless or less risky than tobacco or alcohol.
Data from California, which legalized medical use in 1996 show that teens perceive marijuana and blunts as more socially acceptable and less risky than cigarettes. Exposure to positive messages on therapeutic benefits of marijuana use was associated with a 6% greater odds of marijuana use while peer use was associated with 27% greater odds of use.Similarly young adults in Colorado acknowledged the harmful effects of tobacco use, including secondhand exposure, while exposure to marijuana smoke was perceived as benign.The trend in marijuana legalization may contribute to shifts toward reduces risk perceptions and more permissive norms among young people in the US.Indeed, a 2014 Canadian study with adults found that social normalization of cannabis is driven and reinforced by its perceived widespread use, low incidence of harm from use, and positive social norms surrounding medical use. Canadians were also skeptical of the media’s “exaggerated” portrayal of the harms and risks of cannabis use, although some users did acknowledge health risks, particularly for smoked marijuana. Health risks commonly cited in the public discourse, including respiratory problems, mental health problems, cognitive and memory deficits, were not salient to cannabis users who perceived use was associated with a low incidence of cannabis related harm. Some participants in the study perceived risks of cannabis to be modest compared to tobacco and alcohol.Marijuana use in the United States has been rising since 2002 in both young and older adult populations, while days of use among past year users has also increased. Hall and Pacula’s initial comparisons of young adults in the United States found few differences between use in decriminalization versus prohibition states. Williams and Bretteville-Jensen used the 2001 National Drug Strategy Household Survey to assess the impact of marijuana decriminalization policy on marijuana smoking prevalence in Australia and found that decriminalization is associated with earlier youth marijuana use,and short-term increases in the population prevalence of useLiving in a medical marijuana state was associated with an increased likelihood of initiating marijuana use among young adults, although states with medical marijuana laws had higher rates of use before legalization.
No clear increases have been found since legalization of medical marijuana, especially in youth. Marijuana prevalence among young adults in Colorado went from 21% in 2006 to 31% in 2014 and among adults from 5% in 2006 to 12% in 2014.406 In 2014, 14% of adults were regular marijuana users , with 33% reporting daily use.In Washington young adult use went from 11% in 2011 to 15% in 2013, and older adult use from 4% in 2011 to 8% in 2013.Eighteen percent of young adults in Oregon and 21% in Alaska reported past 30-day marijuana use in 2014, prior to state implementation of retail marijuana laws. In Uruguay, marijuana use has been increasing since 2001, with 23% reporting ever use, 9.3% reporting past year use, and 6.5% reporting current use in 2014 . Of note, since Oregon, Alaska, and Uruguay had not fully implemented marijuana regulatory frameworks these data provide very little information about the direct impact of legalization laws on risk perceptions and use. While previous research argued that marijuana prevalence is unrelated to legalization because higher use rates were generally found prior to legalization,392 data from Denver and Seattle suggest that youth perceptions of risk have decreased and adult use has increased since implementation of retail marijuana laws.480 Moreover, while prevalence was indeed higher than the national average in the four US states that legalized recreational marijuana, liberalizing marijuana laws in 2013 and 2014 has led to dramatic increases in young adult prevalence in Colorado and Washington after the retail market opened. Notably, in Oregon, marijuana use among those 26 years and older nearly doubled between 2006–2007 and 2012-2013 , while national use has increased only slightly .Noncombustible forms of marijuana are increasing in popularity.Even though the use of noncombustible products might be increasing, their overall share is still very low among youth and adults compared to combustible product use in the four US states and Uruguay. Among current marijuana users in Colorado, young adults were more likely to report smoking marijuana than vaporizing and consuming edibles .Cross-sectional data show similar findings among high school seniors with 74% in Washington and 88% in Alaska reporting combustible product use as the preferred mode of consumption.
Similar findings were noted in Oregon in 2015, with nearly 90% of adults and youth reporting combustible marijuana use .In Washington, in 2014 high school seniors were less likely to report oral ingestion , vaporization , or other modes of administration than combustible product use.In Oregon, adults were less likely to report edible use , vaporization , while 25% reported using multiple routes of administration.Multiple administrative routes was most frequent among heavy marijuana users than less frequent users. Among frequent cannabis users in Montevideo,greenhouse tables use of joints and pipes were two of the most widely reported modes of administration in the past 12-months. Other modes of administration that were less popular include: edibles , vaporization , drinks , tinctures , and creams .368 Thus, while consuming edibles and vaporizing marijuana may be less dangerous in terms of cancer, heart disease, and lung disease than using smoked products, smoking remains the dominate mode for consuming marijuana. In addition, it is unknown what the health impacts of these forms of administration are on cardiovascular health or brain function.Marijuana commercialization was associated with a significant increase in annual hospitalizations from 803 to 2,413 in Colorado following the opening of the commercial retail market in 2013. In addition, emergency room visits increased from 739 per 100,000 to 956 per 100,000 ED visits .There was also an increase in emergency room visits for burns, cyclic vomiting syndrome, and marijuana intoxication. At the University of Denver’s burn center, 31 people were treated for marijuana related burns as a result of unexperienced users experimenting with chemical extraction using butane.Some of the increase in hospital utilization could be explained by an increase in new users experimenting with alternative ways to use and produce marijuana.The prevalence of cyclic vomiting syndrome increased after legalization of for-profit medical dispensaries in Colorado in 2010.Since 2012, when retail marijuana laws were implemented, cyclic vomiting syndrome has doubled from 41 per 113, 262 ED visits in to 87 per 125, 095 after medical marijuana was legalized. Legalization of retail marijuana in Colorado was associated with a 44% increase in marijuana-related auto fatalities, from 55 in 2013 to 79 in 2014. In Washington, auto fatalities that involved drivers with active THC in their blood increased by 122.2% from 2010 to 2014 .The interpretation of marijuana-related traffic fatalities is difficult because, unlike alcohol, there is no scientific consensus on what defines “THC impairment,” and THC can be found in the blood or urine several days after use.Legalization may also have resulted in ascertainment bias in that police in Colorado were testing more frequently for THC levels in drivers than prior to legalization. Rather an increase in drivers who tested positive for THC may better explain an increase in marijuana use generally rather than marijuana-impaired drivers specifically. The available epidemiological data on risk perceptions and use patterns from the four US states are limited in their ability to provide a comprehensive overview of the effects of state implementation of marijuana laws because legalization has only been in place for a relatively short period of time. The best that public health authorities can do is provide evidence from the tobacco control experience to have at least an understanding of what potentially the impact of these laws could be on marijuana risk perceptions, use, social norms, and harms associated with use. These shortcomings in the available literature indicate the importance of collecting adequate baseline data before enacting policy change .
Identifing proximal measures of harm with which to measure impacts of legalization would also facilitate evaluating the effects of marijuana policy change.In many ways the state of the marijuana market is similar to where tobacco was at the turn of the 20th Century, before corporatization of the market, with industrialized product design and production and mass marketing.The result was the rise of a sophisticated and politically powerful tobacco industry that led to the death and suffering of hundreds of millions of people worldwide. It took nearly a century to begin to bring the tobacco industry under control as a result of the combined forces of national and international public health advocacy and policy making, as exemplified by the WHO Framework Convention on Tobacco Control.The four US states that have legalized retail marijuana to date have used regulatory regimes largely modeled on alcohol policy regimes. There has not yet been a legalized nationwide market available for entry of major corporations. It is likely that large corporations, including the tobacco industry,with the product engineering and marketing power to quickly transform the market, could capitalize on the opportunities that such a market represents. In part because of relatively low use and the fact that marijuana and tobacco are often used together, the specific health dangers of marijuana are not yet fully defined. We do know that marijuana smoke is toxicologically similar to tobacco smoke and had been identified as a human carcinogen by the California Environmental Protection Agency72 since 2009. There is also evidence of risk of heart and lung disease as well as psychological issues. Other forms, such as edibles, oils, and vaporized marijuana have other risk profiles that are not yet well defined. The question from a policy making perspective is whether to apply the precautionary principle and develop policies to minimize use based on the existing evidence base or wait, likely 20 to 30 years, until the specific risks of marijuana and secondhand exposure have been quantified as precisely as they have been for tobacco today. There is evidence to support the conclusion that without adequate public health controls a newly legalized marijuana market will transform into one modelled on the tobacco market. There are enough similarities between tobacco and marijuana products that the evidence and experience from successful tobacco control programs could form the basis for a public health approach to legalizing marijuana. principles defined in the WHO Framework Convention on Tobacco Control486 could form the basis for a public health approach to legalizing marijuana, which would seek to minimize industry influence in the policy process and to minimize consumption of marijuana products and the associated health risks of a new legal marijuana market.