By way of introduction, I was the first Director of the National Institute of Health’s National Institute on Drug Abuse (NIDA), the United States’ principal agency devoted to scientific research on drugs of abuse, including marijuana. I am currently the President of the Institute for Behavior and Health, Inc., a non-profit organization devoted to reducing illegal drug use, and Clinical Professor of Psychiatry at Georgetown University School of Medicine. I urge you to not underestimate the significant negative public health impacts of marijuana legalization.

In response to the discussion paper, Toward the Legalization, Regulation and Restriction of Access to Marijuana, I would like to share with you some important information specifically related to the discussion of the gateway theory. Marijuana is in fact a “gateway” drug – but importantly, it is not the only gateway drug. Alcohol and tobacco are also gateway drugs. By this I mean that their use is highly correlated with one another and nearly always precipitates the use of other substances. Recent analysis of data from the US National Household Survey on Drug Use and Health (NSDUH) confirm that among young people aged 12 to 17, using one of these three primary drugs of abuse dramatically increases the likelihood of use of the other two, as well as use of other illicit drugs. Similarly, the decision not to use any of these three drugs is negatively correlated with use of the other two drugs (as well as other illicit drugs). This finding has significance for Canada and the US, as well as any other nation considering adding marijuana as a third legal drug for adults. More use of marijuana means more use of other drugs, including the two currently legal drugs. As such, given that the vast majority of substance use disorders, i.e., addiction, can be traced to initiation of substance use during adolescence, there must be significant focus on prevention.

Marijuana is not a harmless drug as it is often perceived to be today. In the US, marijuana accounts for more substance use disorders than any other drug (other than alcohol). Of the 7.1 million Americans aged 12 and older with substance use disorders related to illicit drugs, nearly 60% are dependent on or abuse marijuana (Center for Behavioral Health Statistics and Quality, 2015). The only drug that causes more substance use disorders than marijuana is alcohol.

Making marijuana more easily accessible and subsequently increasing its use by the public should be of serious concern to the Canadian government and its citizens. Recent research has shown that daily or near-daily marijuana users in the US consume most of the drug, with the poor and less-educated representing a disproportionate number of marijuana users (Davenport & Caulkins, 2016). Protecting the vulnerable populations – from youth to the disadvantaged – must be a national and global priority.

I urge you to support policies and programs that seek to reduce drug use, including marijuana use, and to improve public health. Making marijuana more accessible and its use more acceptable is not in the interest of public health.

Editors Note: The New York Times opinion series “Room for Debate” asked if marijuana should be legalized in the face of today’s heroin and opioid crisis and if it is a gateway drug. IBH President Robert L. DuPont, MD contributed to the series stating that marijuana use is positively correlated with other drug use; marijuana users consume more legal and illegal drugs than non-users. Rather than legalize drugs, effective prevention is needed. He clearly states that establishing marijuana “as a third legal drug, along with tobacco and alcohol, will increase drug abuse, including the expanding opioid epidemic.”