Late last month Donald Trump’s administration declared the rising death rate from opioid overdoses a national public health emergency. Thirty-three thousand lives were lost to this scourge in 2015, and early reports from the Centers for Disease Control and Prevention paint an even bleaker picture for 2016.

Policymakers working for the president are doubling down on a policy aimed at restricting opioids. But this policy isn’t working. In fact, it might even be contributing to abusers’ switch to more potent drugs such as heroin in recent years.Yet there is an approach that can truly curb the rising rate of overdose deaths that is staring them right in the face: legalizing marijuana.

According to research published earlier this month in the American Journal of Public Health, Colorado’s legalization of recreational marijuana in 2014 coincided with a 6.5 percent reduction in opioid overdose deaths. The researchers studied the opioid overdose rate in the state from 2000 to 2015, and found that after 14 years of a steady rise in opioid overdose deaths, the rate decreased by an average of 0.7 deaths per month.

This is not the first study to find that marijuana is associated with a drop in the use and abuse of opioids and other dangerous drugs. A 2014 study examined states where marijuana was available for medical use between 1999 and 2010 and found, on average, a 25 percent reduction in annual opioid overdose mortality compared to states in which marijuana was illegal. Researchers at the RAND Corporation found similar results in 2015. And in June of this year, a study of chronic pain patients by the University of California at Berkeley found that 97 percent of patients decreased opioid consumption as a result of using medical marijuana, and 81 percent found marijuana alone was more effective than using both marijuana and opioids.

Clearly some patients require fewer opioids to treat their pain when they have access to marijuana. But Colorado’s encouraging data reflects the impact of recreational marijuana access—not medicinal. These new findings suggest the possibility that people seeking to get “high” on mind-altering drugs, when given the opportunity, tend to choose the safer option—when it’s legal and available from sources other than black market drug dealers. There might even be a pharmacological basis to these findings. Research published in 2013 in the journal Addiction Biology suggests cannabis “interferes with brain reward mechanisms responsible for the expression of the acute rewarding properties of opioids…”

And a 2017 article by researchers at Mt. Sinai School of Medicine points to animal models that suggest cannabidiol, found in cannabis, might reduce withdrawal symptoms as well as opioid-seeking behavior. This is an area that needs further investigation, but one thing is clear: marijuana availability is associated with a decrease in opioid use, abuse, and overdose.

Opponents of marijuana legalization have claimed for years that marijuana is a dangerous “gateway drug” that leads users to more treacherous and addictive drugs, like heroin. These claims are premised on the fact that most users of heroin, cocaine, and other dangerous drugs also report that they use marijuana. But they also report the use of tobacco and alcohol. Critics of the gateway theory are quick to point out that correlation is not the same as causation. Now there’s evidence of a negative correlation between marijuana and harder drugs. More marijuana correlates with less opioids.

Even proponents of opioid restriction agree that Medication-Assisted Treatment is a useful tool for dealing with opioid addiction. This employs medications such as methadone, suboxone, and naltrexone to wean addicts away from opioids. Marijuana’s potential for medicinal use has been recognized by healthcare professionals—and realized by patients—for many years. Now, it offers the potential for averting and treating opioid abuse.

Rather than a gateway, marijuana may be an off-ramp to opioid abuse. Opponents of marijuana legalization should keep that in mind before they try to close this ramp off.

Dr. Singer practices general surgery in Phoenix, AZ and is a Senior Fellow at the Cato Institute