As marijuana use was considered illegal for most yearly examinations in CARDIA, use may have been under reported. However, at each examination, marijuana use was self-reported , collected at a research site , and participants’ responses were confidential. The route of administration of marijuana can also affect the onset, intensity, and duration of the psychoactive effects, as well as organ systems. Investigations into marijuana use via other routes of administration may provide novel additional insights, including the latter, which was not present during the time points in the current study but is becoming more widely used. Additionally, this study examined acute exposure to marijuana , compared to hyperacute exposure and investigations into DNA methylation changes due to hyperacute exposure may provide further insight into the acuity of exposure on epigenetic factors. And lastly, although CARDIA is a diverse cohort, Black and White participants were sampled from four centers across the US. As such, additional studies from more diverse populations across different geographical locations will enable for better generalizability of the findings presented here.Legalization for medical purposes has been accompanied with increased daily use and marijuana use disorders among US adults . Approximately 15% of the US adult population used marijuana in some form in 2017 . Between 2016 and 2017, past-month use of marijuana increased nearly 2% among adults aged 18 to 25 years and 1.2% among adults 26 years and older . Additionally, national surveys suggest the perception of ‘‘great risk’’ from weekly marijuana use dropped from 50.4% in 2002 to 33.3% in 2014 and has dropped further since . Recent national surveys also demonstrate that the public attributes benefits to marijuana that are not supported by existing scientific evidence,indoor weed growing accessories such as relief from anxiety, stress, and depression, improved appetite, and improved sleep .
It is unknown whether adult residents of states where marijuana has been commercialized for recreational use are more likely to attribute benefits to marijuana use. Given the growing body of evidence that adverse consequences are associated with regular marijuana use , determining whether residents of recreational states perceive marijuana use differently than residents of states without commercial legalization is an important consideration and may inform the needs for more investment in communications of potential risks to the public. In this study, we examine the differences in beliefs about marijuana use and rates of use across states defined by their marijuana legalization status .Survey questions were developed by identifying gaps in existing federally funded national surveys, including the National Survey on Drug Use and Health and Monitoring the Future , and drafting questions to address those gaps. Questions were refined through interviews with marijuana industry professionals, dispensary staff, marijuana distributors, and mental health and substance use disorder experts. Survey items developed included individual opinions on the risks and benefits of marijuana use, comparisons of risks and benefits of marijuana to other psychoactive substances, and the form, amount, and frequency with which individuals use marijuana. In total, the survey included 29 questions assessing beliefs about the risks and benefits of marijuana and 54 questions assessing marijuana use. Answer options for all opinion questions used Likert scales to allow participants to respond with the answer most closely aligned with their beliefs. All questions were written at an 8th-grade reading level and were tested on a convenience sample of 40 adults to ensure readability and construct validity. Full details on survey development have been previously published . The survey tool is available in the supplementary material .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 KnowledgePanel —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. Participants are provided with no more than 6 surveys a month and are expected to complete an average of four surveys a month . Sampling was stratified by legalization status of marijuana in the state of residence . California residents and young adults aged 18 to 26 years old were over sampled to facilitate a future investigation into the role of recreational legalization on use patterns among young adults in California. Sampling weights were provided by GfK.The response rate, determined using methods outlined by the American Association for Public Opinion Research, was the ratio of respondents to all potential participants . Characteristics of the survey respondents were weighted using weights provided by GfK to approximate the US population based on age, sex, race, ethnicity, education, household income, home ownership, and metropolitan area. All analyses used weighting commands using the weight variable provided by GfK to generate national estimates. We first compared the sociodemographic characteristics of our respondents to that of the NSDUH—an annual, federally funded epidemiologic survey . We then compared views and forms of marijuana use of residents across recreational, medical, and nonlegal states using chi-square statistics. Finally, we reported the prevalence of different forms of use stratified by legalization status of states and the associated 95% confidence interval . In supplementary analyses, using logistic regression, we examined views of residents of recreational states compared with other states after adjusting for baseline demographic characteristics including age, sex, race, employment status, and household size. All analyses were performed with R statistical software .
The response rate of the survey was 56.3% and did not vary by status of legalization in state of residence . The rate of missing or refused questions ranged from 0% to 3.9%. The sample was 52% female, 64% white, 12% black, 16% Hispanic, and 8% other race with a mean age of 48 years. Residents of the 3 state types did not differ by age. The residents of recreational states were predominantly white and less diverse than other state types . The residents of recreational states had higher rates of education and higher income levels compared with other state types. Sociodemographic characteristics of the respondents were largely similar to those of NSDUH,cannabis trimming though our sample had a slightly higher average income .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 .The belief that marijuana use was associated with the development of addiction was similar across states . 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, 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 . 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 .