Memo to Homeland Security: Marijuana is not a gateway drug. Science says so.

Department of Homeland Security Secretary John Kelly alleges that marijuana is a “dangerous gateway drug that frequently leads to the use of harder drugs.”

In fact, the available science concludes just the opposite.

{mosads}More than half of American adults have tried cannabis, according to data compiled by the Centers for Disease Control. Statistically, the overwhelming majority of these individuals never go on to try another illicit substance, an empirical reality that persuaded investigators at the RAND Corporation to conclude, ”[M]arijuana has no causal influence over hard drug initiation.”

Moreover, by the time these individuals reach age 30, most of them have significantly decreased their cannabis use or no longer indulge in the substance at all.

Even more noteworthy is the reality that cannabis appears to act as a substitute or, in some cases, an exit drug for those struggling with drug abuse.

For example, in jurisdictions where marijuana use is legally regulated, researchers have reported year-over-year declines in opioid-related abuse, hospitalizations, and mortality.

According to data published in the esteemed Journal of the American Medical Association, deaths attributable to both prescription opiates and heroin fell by 20 percent within a year following marijuana legalization and by 33 percent within six years.

Overall, the study’s investigators concluded, “States with medical cannabis laws had a 24.8 percent lower mean annual opioid overdose mortality rate compared with states without medical cannabis laws.”

Other studies have reported similar declines in the use of other drugs in jurisdictions where cannabis access is legally permitted.

According to a just-published review of the medical histories of over 1,500 patients residing in medicinal marijuana states, cannabis therapy was associated with significant reductions in subjects’ use of anti-anxiety medications, sleep aids, and anti-depressants. Forty-two percent of study subjects also acknowledged reducing their alcohol intake. The findings are similar to those from Canada, where medical access to marijuana is legal nationwide, and patients report using cannabis in place of opiates, benzodiazepines, and antidepressants, as well as in lieu of alcohol and tobacco.

A 2016 US study assessing prescription drug spending in multiple medical marijuana states over a three-year period similarly determined that “when a medical marijuana law went into effect, prescribing for FDA-approved prescription drugs … fell substantially.”

Writing this month in the journal Addictive Behaviors, investigators at the University of Montreal and the University of British Columbia contend that cannabis use curbs cravings for cocaine. They report: “In this longitudinal study, we observed that a period of self-reported intentional use of cannabis … was associated with subsequent periods of reduced use of crack [cocaine]. … Given the substantial global burden of morbidity and mortality attributable to crack cocaine use disorders alongside a lack of effective pharmacotherapies, we echo calls for rigorous experimental research on cannabinoids as a potential treatment for crack cocaine use disorders.”

Similar data exists for those addicted to opiates. For example, researchers at New York’s Columbia University reported, “[Opioid dependent] participants who smoked marijuana had less difficulty with sleep and anxiety and were more likely to remain in treatment as compared to those who were not using marijuana.”

In light of this scientific evidence, combined with a growing number of Americans’ first-hand experience with cannabis, it is hardly surprising that public confidence in the supposed ‘gateway theory’ is waning.

According to survey data compiled in 2016 by YouGov.com, fewer than one in three US citizens agree with the statement, “[T]he use of marijuana leads to the use of hard drugs.” Among those respondents under the age of 65, fewer than one in four agree.

Public opinion data provided earlier this week by Yahoo News finds even less support, with only 14 percent of adults expressing “significant concern” that cannabis “leads to the use of other drugs.”

In short, both scientific and public opinion reject the contention that marijuana use promotes the use of other drugs. It’s high time that public officials similarly put this myth to rest.

Paul Armentano is the deputy director of NORML (the National Organization for the Reform of Marijuana Laws) and an adviser for Freedom Leaf. He is the co-author of the book “Marijuana Is Safer: So Why Are We Driving People to Drink?” (Cheslea Green, 2013) and author of the book “The Citizen’s Guide to State-By-State Marijuana Laws” (Whitman Press, 2015).

The views expressed by contributors are their own and are not the views of The Hill.