Recreational pot — legalized in Washington, D.C. on Thursday and decriminalized Tuesday in Alaska — is less dangerous than both alcohol and tobacco, scientists assert.
The safety of marijuana versus booze is not a new claim but, for the first time, researchers measured the potential harm of these drugs in a more quantitative way — that is, by comparing a lethal dose to how much of the substance is typically consumed socially.
Their findings showed the dangers of marijuana "may have been overestimated in the past", while the risk of alcohol has been "commonly underestimated," researchers said.
The report, published in Scientific Reports at the end of January, compared the potential of death from the typical, recreational use of 10 drugs: marijuana, alcohol, tobacco, heroin, cocaine, ecstasy, methamphetamine, diazepam, amphetamine and methadone. Marijuana was, by far, found to be the safest, even when compared to alcohol and cigarettes.
The new study comes as more Americans push for the right to smoke weed legally.
Lead author Dirk Lachenmeier told NBC News the findings, "confirm earlier results of other study groups [but] with completely different methodology." And while his results may not be surprising, "the absolute differences in riskiness between substances" was even higher than expected.
Alaska has joined two other states in legalizing recreational marijuana. An additional 23 states allow for medical marijuana prescriptions and use. Oregon passed a legalization initiative that will go into effect in July. A law to legalize marijuana in the Washington D.C., approved by voters last fall, will go into effect at 12:01 am on Thursday, unless Congress steps in last minute.
The U.S. Drug Enforcement Administration ranks controlled substances according to five "schedules." Marijuana, along with drugs like heroin and LSD, is a Schedule I drug, meaning it is considered to have the highest potential for abuse and be the "most dangerous."
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Because alcohol and tobacco are legal, they are not controlled substances, and not subject to DEA scheduling.
For years, medical-marijuana proponents and legalization advocates have deployed the battle cry that cannabis is far safer than alcohol. And they've long contended it's hypocritical for a nation to allow massive alcohol marketing and sales while banning marijuana.
Tobacco use is considered the leading preventable cause of death in the U.S. and chronic alcohol use has been linked to everything from heart disease to cancer. According to the CDC, one in 10 deaths among working-age adults can be attributed to excessive alcohol use and alcohol poisonings account for more than 2,000 American deaths every year.
Meanwhile, most experts say there has never been a documented overdose death from marijuana use in someone without an underlying condition.
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That is not to say that marijuana use isn't potentially harmful.
Chronic marijuana use has been linked by some researchers to lung problems, dependence and early onset psychosis. There is also considerable concern over the impact of marijuana use on the developing adolescent brain. One study, published in the Proceedings of the National Academy of Sciences, found that regular marijuana users lost an average of six IQ points by adulthood.
In January, the American Academy of Pediatrics reaffirmed their opposition to legalizing marijuana for recreational or medical use.
"We really don't know the impact of legalization on youth access and youth use," said Dr. Seth Ammerman, an adolescent medicine specialist at Stanford and author of the AAP policy statement.
Since legalization last year in Washington and Colorado, pediatric marijuana-related calls to poison-control centers in those states have doubled. Experts are especially concerned about edibles like pot brownies or lollipops, which are appealing to young children and may lead to accidental ingestion.