All analyses were performed with R statistical software .Overall, residents of states where marijuana was legalized for recreational purposes were more likely to endorse the belief that marijuana had benefits compared with residents of other states . Specifically, residents in recreationally legal states were more likely to believe marijuana could be beneficial for pain management ; provide relief from stress, anxiety, or depression ; and improve appetite . Pain management was endorsed as the most important benefit regardless of state of residence . Residents of nonlegal states were more likely to endorse the belief that marijuana had no benefits compared with those in recreationally legal states . Multivariate analyses confirmed that residents of recreational states were less likely to believe marijuana had ‘‘no benefits’’ and more likely to believe that marijuana use had benefits in pain management, helped with reducing or stopping other medications, provided relief from stress, anxiety, and depression, improved sleep and appetite, and improved creativity compared with residents of medical and nonlegal states after adjusting for baseline characteristics .Residents of recreational, medical, and nonlegal states all endorsed addiction as the most important risk associated with use . Multivariate analyses revealed that residents of recreational states were more likely to believe that marijuana use impaired memory, and also caused a decrease in intelligence and energy compared with residents of other medically legal and nonlegal states after adjusting for baseline characteristics .Residents in recreational states were significantly more likely to believe that smoking one marijuana joint a day is somewhat or much safer than smoking 1 cigarette a day . Residents of recreationally and medically legal states were more likely to believe second-hand marijuana smoke was somewhat or much safer than second-hand tobacco smoke .

Opinions regarding other relevant public health concerns were largely similar across states: most residents,plant nursery benches regardless of legal status in state of residence, agreed that it is unsafe for children and adults to be exposed to second-hand marijuana smoke, and that marijuana use was unsafe for pregnant women. Multivariate analyses confirmed that residents of recreational states were more likely to believe that smoking 1 marijuana joint a day was safer than smoking 1 cigarette a day compared with residents of other medically legal and nonlegal states after adjusting for baseline characteristics . Residents of recreational states were also more likely to believe second-hand smoke from marijuana was safer than second-hand smoke from tobacco compared with residents of other medical and nonlegal states after adjusting for baseline characteristics .In this national study, we found that residents of states that had legalized recreational marijuana use more commonly attributed some benefit to marijuana than residents of medically legal or nonlegal states. We also found that the perception of risks from marijuana use was similar across states. In addition, we found that residents of states where marijuana was legalized were more likely to believe that marijuana smoke was less harmful than tobacco smoke. Finally, use of all forms and multiple forms of marijuana was more common among residents of recreationally legal states. Several national surveys, including the NSDUH and MTF, assess individual risk perception of marijuana use among national samples, and recent research suggests that risk perception has decreased nationwide . Previous research demonstrates that marijuana legalization is associated with decreases in risk perception, as evident from studies examining California pre and post medical legalization in 1999 . More recent research supports this assertion , and while research into the role of recreational legalization specifically is limited, initial data in adolescents suggest recreational legalization has been associated with a considerable decrease in risk perception .

While such surveys have adequately examined the decrease in risk perception associated with marijuana, there exists no detail on the types of risks individuals associate with marijuana use or potential benefits individuals assign to marijuana use. Our results show that residents of states where marijuana has been legalized for recreational use have an overall more favorable view towards potential benefits of marijuana use and were more likely to attribute benefits to marijuana use that are not supported by evidence. For example, a majority of respondents endorsed pain relief as a benefit of marijuana use, despite only limited evidence supporting its effect in managing chronic neuropathic pain and no evidence in treating other types of chronic pain . There is no evidence currently available that suggests second-hand marijuana smoke is safer than tobacco smoke and some evidence suggesting it is toxic . There is no data suggesting that marijuana is an effective and safe treatment for insomnia . When taken in context with previous research demonstrating the decrease in risk perception associated with marijuana use, our findings are significant as they illustrate the need for targeted public health campaigns to combat misinformation specifically in states with recreational marijuana legalization. We found that residents of recreationally legal states expressed less concern regarding second-hand marijuana smoke compared with second-hand tobacco smoke, and were more likely to believe that smoking marijuana is somewhat or much safer than smoking tobacco. These differences in perception are concerning, given the evidence that inhalation of particulate matter in any form is associated with increased cardiovascular risk . The perception that marijuana smoke is relatively safe compared with tobacco smoke has been perpetuated by the spread of inaccurate information on the internet . Some highly frequented internet sites suggest that smoking marijuana has many health benefits, such as improvement of lung health or the slowing of Alzheimer symptoms .

There is currently no data to suggest that smoking marijuana improves lung health. On the contrary, recent evidence demonstrates smoking marijuana is associated with coughing, wheezing, and sputum production . The lack of a clear federal public health response to the growing legalization of marijuana and proliferation of pro-marijuana marketing has left a vacuum that is filled by commercial interests . Unlike the tobacco industry, the marijuana industry has remained largely unchallenged by a coordinated regulatory response, and is aggressively advertising its product in states with rapidly expanding commercial markets . Over half of adults living in states with recreational marijuana are frequently exposed to pro-marijuana advertising in numerous forms , and research indicates that greater exposure to pro-marijuana advertising is associated with heavier marijuana use among adolescents and heavier use among adult persons who use . More stringent regulations of marijuana product marketing, and also a cohesive public health messaging campaign, are necessary to combat misinformation and communicate the potential risks associated with marijuana use so consumers can make informed choices about use. With the exception of smoking rates, which were roughly equivalent among residents in recreationally legal and medically legal states, prevalence of use among all forms of marijuana and use of multiple forms of marijuana was higher among residents in recreationally legal states. This is not surprising, given that novel forms of marijuana are more accessible in states with robust recreational markets. For example,metal greenhouse benches in the first year with an active recreational marijuana market, Colorado dispensaries sold 4.81 million units of edible cannabis product . The popularity of marijuana products in forms other than smoking is a cause for some concern as such products are increasingly available with THC content at high levels not yet studied. Previous research suggests that some edible products exceed state-mandated THC thresholds and can reach as high as 7000 mg per package . Given the growing popularity of marijuana in forms like edibles or extracts, increased focus should be directed towards understanding the health effects of THC at such concentrated levels. In the absence of evidence of harms, states may be reluctant to more stringently regulate the form and content of edible products. There are several limitations to this study. The generalizability of our results may have been limited by the use of an internet survey as the population who choose to join an ongoing internet panel may be different from individuals who choose not to participate. However, GfK’s KnowledgePanel has demonstrated no evidence of non-response bias in the panel on core demographic and socioeconomic variables . We did not conduct reliability testing of the survey items. As a result, it is possible the interpretation of our questions might differ between participants. For example, though pain management was endorsed as the most important benefit across residents of all states, we did not distinguish between types of chronic pain, and this may have been interpreted differently between participants. Additionally, we did assess the extent of individual marijuana use among participants, medical reasons for use among marijuana users, and sources of information regarding beliefs about marijuana. However, the data were not sufficiently relevant when stratified by state legalization status.

Furthermore, it is important to note that we did not differentiate between state legal status beyond the designation of ‘‘recreationally legal, medically legal, or nonlegal,’’ and marijuana accessibility can vary greatly within states with the same legal status due to differences in state-based implementation. Nonetheless, we found clear differences in opinions of residents of recreationally legal states compared with other states. Finally, the study was cross-sectional. Therefore, it is unknown if people in states where marijuana was legalized for recreational use developed their beliefs before legalization, which then led to legalization in their state, or if the opinions assessed in this survey were a result of recreational legalization of marijuana.The prevalence of marijuana use has increased in the past decade in the United States population and worldwide. In tandem with increasing marijuana use, there has also been a substantial drop in the public’s perception of risks from marijuana use in the US and other Western countries.Moreover, the marijuana industry has experienced tremendous growth in the past decade and is projected to exceed $57 billion in annual revenue within the next decade.In tandem with the growth in marijuana marketing, sales, and use, there has been a proliferation of misinformation.National surveys suggest the perception of Bgreat risk^ from weekly marijuana use has dropped from 50.4% in 2002 to 33.3% in 2014 and has dropped further since.A recent national survey demonstrated that the public attributes benefit to marijuana without any evidence to support such beliefs . Moreover, recent data also suggests that many Americans believe that marijuana has no risks and that it prevents health problems.The main drivers of this favorable perception in the US are unclear, but it is likely multi-factorial and includes the liberalization of medical marijuana laws and promotion by advocacy organizations and business interests. For example, Business Insider, a website with an audience of over 100 million visitors a month,recently touted the ability of marijuana to Breverse carcinogenic effects of tobacco and improve lung health.^ The source research article cited by Business Insider did not support such a claim.In addition, legalization has been accompanied by the commercialization of marijuana, with projections estimating that marijuana sales will exceed $25 billion by 2025.There is overt marketing to consumers of marijuana on the Internet and social media with inadequate regulatory oversight.It is possible that sources of information are playing a role in furthering misinformation among the public, which in turn is resulting in decreases in risk perception, particularly among adolescents.Determining the public’s main sources of information about marijuana use is essential to curbing misinformation and improving public health outcomes. In this national survey of US adults, we examined where US adults receive information about marijuana. We also examined whether the sources of information were associated with believing unsupported claims about marijuana.We conducted a survey of a nationally representative sample of 16,280 US adults on risks and benefits of marijuana use. The survey was conducted using Knowledge Panel , a nationally representative panel of civilian, non-institutionalized US adults aged 18 years and older that has been used to survey public opinion since 1999. GfK created a representative sample of US adults by random sampling of addresses. The address-based sampling covers 97% of the country and encompasses a statistical representation of the US population. Households without Internet access are provided with an Internet connection and a tablet to ensure participation. All participants in the panel are sampled with a known probability of selection. No one can volunteer to participate and are instead selected randomly by GfK based on address.