Since 2012, nine states and Washington D.C. have legalized marijuana for adults’ use, and the harms prohibitionists predicted have not come to pass. Despite the success of these programs, there are still misconceptions about marijuana and the impact of legalization.
Marijuana is not a gateway drug.
Numerous studies have found that marijuana use does not lead to the use of other more dangerous substances.[ Most recently, the National Academies of Sciences, Engineering, and Medicine released a report that found there is no physiological “gateway” effect. And the vast majority of people who have used marijuana never try other illegal drugs.
The illicit market, however, can expose marijuana consumers to other drugs, and prohibiting marijuana can incentivize consuming more dangerous substances like opiates and alcohol.
In fact, a recent review found: “Research suggests that people may be using cannabis as an exit drug to reduce use of substances that are potentially more harmful, such as opioid pain medication.”
There is no evidence that legalization leads to an increase in traffic fatalities.
Opponents of regulating marijuana frequently suggest that “marijuana-impaired” driving has led to more traffic fatalities. In making that claim, opponents point to data that simply indicates more drivers involved in fatal crashes tested positive for THC. But those drivers may not have been at fault or impaired in any way — THC can stay in a person’s system for weeks. Opponents also ignore that more drivers involved in collisions are being tested for marijuana, skewing the results.
A study published in the American Journal of Public Health found, “Three years after recreational marijuana legalization, changes in motor vehicle crash fatality rates for Washington and Colorado were not statistically different from those in similar states without recreational marijuana legalization.” Fatalities per million miles drivenwere below the national average in Colorado and Washington, both before and after legalization.
Teens’ rate of marijuana use does not increase after legalization.
In February 2017, the Colorado Department of Public Health and Environment reported the rate of marijuana use among adolescents “has not changed since legalization either in terms of the number of people using or the frequency of use among users. . . Based on the most comprehensive data available, past-month marijuana use among Colorado adolescents is nearly identical to the national average.”
The state-run Washington State Healthy Youth Survey of 37,000 middle and high school students found no increases in the rates of marijuana use for any of the age groups surveyed from 2012-2016.
The head of the National Institute on Drug Abuse (NIDA), Nora Volkow, has acknowledged that many people predicted, “that there would be an increase in the pattern of use of marijuana among teenagers and we are not seeing it.”
 A 1999 White House commissioned Institute of Medicine study found that marijuana: “does not appear to be a gateway drug to the extent that it is the cause or even that it is the most significant predictor of serious drug abuse; that is, care must be taken not to attribute cause to association.”In June 2015, the American Journal of Drug and Alcohol Abuse published research that concluded marijuana use itself was not a risk factor for use of other substances.
 About half of all Americans have used marijuana at some point in their lives. Only 1.9% have tried heroin and 15% have tried cocaine. Gallup Poll, July 19, 2017; U.S. Office of Applied Studies, 2015 National Survey on Drug Use and Health: Detailed Tables(last accessed August 28, 2017).
 University of British Columbia, “Marijuana could help treat drug addiction, mental health, study suggests,” ScienceDaily, November 16, 2016.
 JD Aydelotte, et al., “Crash Fatality Rates After Recreational Marijuana Legalization in Washington and Colorado,” Am. J. of Public Health, August 2017.
 See Insurance Institute for Highway Safety, “General Statistics, State by State,” at http://www.iihs.org/iihs/topics/t/general-statistics/fatalityfacts/state-by-state-overview.
 Colorado Department of Public Health and Environment. “Monitoring Health Concerns Related to Marijuana in Colorado: 2016. Changes in Marijuana Use Patterns, Systematic Literature Review, and Possible Marijuana-Related Health Effects,” 2017.
 Washington State Healthy Youth Survey, 2012 to 2016, past 30-day use. http://www.askhys.net/FactSheets
 Sifferlin, Alexandra, “High School Seniors Now Prefer Marijuana to Cigarettes,” Time, December 15, 2015.