Every opponent of legalization has a favorite argument. Cannabis is a gateway drug. Marijuana is as addictive as cigarettes. Toking makes you less intelligent.

Marijuana Pipe and JointsThese claims are pervasive, and they’ve guided American drug policy for decades. But a new study finds that almost every “scientific” argument against marijuana is bunk.

The International Centre for Science in Drug Policy, a pro-reform research group, released the study in August. They examined several of the most common claims and declared most of them provably false.

Marijuana as a gateway drug

Take, for example, the belief that marijuana is a “gateway” and leads to the use of harder drugs. This point of view, while in retreat, is still popular around the world.

Researchers reviewed the scientific literature and concluded this claim isn’t true. Repeated studies have demonstrated that tokers are more likely than others to try hard drugs, but also that cannabis doesn’t cause the leap; more likely, it’s a factor of personality, environment, and genes.

Indeed, the researchers behind the new report say lawmakers and healthcare providers often confuse correlation with causality. The fact that marijuana users are more likely to try other drugs doesn’t necessarily mean one fact causes the other, only that they have connections at the statistical level.

Marijuana as a cause of schizophrenia

This problem also arises in the argument that cannabis causes schizophrenia, or at least brain adaptations that are similar to schizophrenia. No study has ever proved that marijuana use actually causes psychotic disorders.

“While scientific evidence supports an association between cannabis use and schizophrenia, a causal relationship has not been established,” researchers wrote in the report, titled “State of Evidence: Cannabis Use and Regulation.”

The scientists did determine that there is at least a kernel of truth to some anti-cannabis claims. The contention that the drug is “300 to 400 percent” more potent today than it was 30 years ago, for example, contains some fact: Marijuana really is measurably stronger, though nowhere near as much as the claim suggests.

Interference with cognitive function

Likewise, assertions that cannabis interferes with cognitive function are partially true, the report found. But there is little data to suggest this effect should be especially troubling.

“While the evidence suggests that cannabis use (particularly among youth) likely impacts cognitive function, the evidence to date remains inconsistent regarding the severity, persistence, and reversability of these cognitive effects,” the researchers wrote.

Marijuana use and drug policy

Is Marijuana AddictiveThey shot down several other claims regarding marijuana use and drug policy, including:

– Cannabis is as addictive as heroin: In reality, 23 percent of heroin users become addicted to that drug while just 9 percent of marijuana smokers develop a dependence.

– Using marijuana can cause fatal damage to the coronary system: In fact, there is no reliable evidence that cannabis weakens the heart, clogs the arteries, or otherwise damages the circulatory system.

– Toking lowers IQ by as many as 8 points: There is simply no data to support this widespread belief. Some studies have found a mild, temporary dip in IQ among some users when high, but the proof is weak at best, and any such effect quickly wears off.

Marijuana Bud– Marijuana reform will only make the drug easier to get, leading to a greater number of addicts and underage users: Actually, the best studies suggest even full legalization has no effect on how many teens use cannabis.

– Regulation doesn’t cut down on crime: This simply isn’t accurate. Science has conclusively shown that the vast majority of “drug crime” stems not from use of any drug but rather from the criminal enterprise that thrives under prohibition. And current evidence suggests that’s exactly what’s happening, as certain crime rates are in fact dropping in places where cannabis is legal.

– Under legalization, stoned driving will be a major problem: Any state trooper can tell you cannabis isn’t a serious problem on the streets. It’s alcohol you have to worry about. Indeed, studies show driving high is only twice as dangerous as driving sober, while drunk driving is 13 times as risky.

– The legal marijuana industry is rapidly evolving into the next “Big Tobacco”: There really isn’t any evidence to support this claim, though there isn’t much to refute it, either. In any event, states that adopt legalization have the regulatory power to prevent this from happening.

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