WSU study: Babies of cannabis-using rats show negative cognitive effects

Because they have the time, researchers at Washington State University tested the effects of marijuana on pregnant rats, since the drug is the most commonly used illicit substance among pregnant women.

This wasn’t simply a case of a college students blowing smoke at their pet rats during a party. It was an actual study. Researchers were totally wearing lab coats at the time.

“We were interested in looking at the effects of prenatal cannabis exposure in a rodent model of maternal cannabis use,” Assistant Professor Ryan McLaughlin told KIRO Radio. “We’re trying to look at the long-term repercussions of using cannabis during pregnancy and how it might effect the offspring and their cognitive functioning in adulthood.”

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In the study, researchers exposed pregnant rats to cannabis vapor twice per day, once in the morning to take the edge off and once in the early evening, presumably when the rats got off work. The researchers then waited for the mothers to give birth — which only takes 21 days for rats, as opposed to nine long months for humans — and then another 70 days for the babies to grow up to full-term adults.

That’s when they put the new adult rats into little, probably horrifying conditioning chambers, and measured their cognitive responses using a system of levers, lights, and sugar pellet rewards. While the rats managed the first round of tests, they did struggle during the second when learning new strategies were involved.

“What we found essentially in our task was that this is where the cannabis exposed animals were impaired, in that they took significantly more trials to learn this new strategy,” McLaughlin said. “It’s important to take this data with a grain of salt, but at the same time, I do want to stress that we really don’t know what cannabis is doing to developing offspring during these developmental periods.”

“It isn’t necessarily a harmless drug,” he said. “There are harms associated with this drug, especially when it interferes with a system that’s very important in neuro-development.”

So don’t smoke marijuana while you’re pregnant, but you already knew that. Don’t give it to your pregnant rat, either.

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