PunditFact checks claim about marijuana lowering I.Q.

Over the weekend, the nation's "newspaper of record" came out in favor of legalizing marijuana. In an editorial, The New York Times called for the federal government to end the 40-year-old ban on marijuana and let states decide about the issue for themselves.

Nearly two dozen states have moved to loosen the reins on marijuana. In November, voters in Florida will decide on a ballot measure legalizing medical marijuana.

On Sunday's "Meet the Press," Washington Post columnist Ruth Marcus said she was generally OK with letting states decide about marijuana use, but worried about pot being easily available -- especially for teenagers.

"The best evidence is that you lose -- if you use marijuana as a teenager regularly -- eight I.Q. points," said Marcus. "I don't know about the rest of the table, but I don't have eight to lose."

PunditFact decided to check Marcus' claim about marijuana use and intelligence tests. Although Marcus didn't respond to its messages, the organization thinks she was citing a 2012 study from Duke University. Researchers studied nearly every child born in a small town in New Zealand since the 1970s. They gave them I.Q. tests as teenagers then another later in life. They asked about their marijuana, alcohol and other drug use. The study concluded that those who regularly smoked marijuana did lose, on average, eight I.Q. points.

Another scientist decided to take another look at Duke's results and came up with different results.

"What they found was that, yes, this group of people lost eight I.Q. points," said PunditFact editor Aaron Sharockman. "But they looked at the same study then looked at socioeconomic status -- essentially how much money you have and how much money you're making. And they found the same result. Poorer people, essentially, lost eight I.Q. points as well."

It's not clear at this point if marijuana use was the cause of lower I.Q. in the New Zealand town. But since Marcus basically said this was settled science when the debate continues, PunditFact rated her claim "Half True."

Support is growing for marijuana:

Florida voters back marijuana

Colorado mom fights medical pot in Florida

Sheriffs against medical pot

Did Snoop Dog smoke in White House?

Campaign to legalize marijuana in Florida


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