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Three studies in rodents suggest prenatal exposure to the drug may pose risks for infants
DANA G. SMITH NOVEMBER 18, 2018
This article was originally published by Scientific American.
One recent study revealed that in 2016 7 percent of pregnant women in California used marijuana, with rates as high as 22 percent among teenage mothers. In Colorado 69 percent of dispensariesrecommended the drug to pregnant women to help with morning sickness.
… prenatal drug exposure can be harmful to unborn babies. Previous research has shown infants exposed to cannabis in the womb are 50 percent more likely to have a lower birth weight. Now three new studies presented Tuesday at the Society for Neuroscience annual meeting here suggest prenatal cannabis exposure—at least in rodents—could have serious consequences for fetal brain development.
In one study researchers at Washington State University in Pullman showed rat pups born to mothers exposed to high amounts of cannabis vapor during pregnancy had trouble with cognitive flexibility. Twice a day the scientists filled the pregnant rats’ containers with marijuana vapor from an e-cigarette, elevating levels of the psychoactive chemical THC (tetrahydrocannabinol) in the rats’ blood to roughly the human equivalent of smoking a joint. After the pups grew up the researchers trained them on a task that measured their ability to think flexibly and learn new rules. The young rats first learned to follow a light cue to push one of two levers in order to receive a sugary treat. The next day, pushing only the left lever would deliver the reward, regardless of which side the light had been on.
The rats exposed to cannabis in utero learned the first rule (following the light cue) without a problem, but they took significantly longer to learn the new rule (pushing the left lever) than did rats not exposed to the drug. The cannabis-exposed rats also made many more mistakes on the second day.
In a similar study, scientists at Auburn University in Alabama found rats born to mothers that had been injected with a low, continuous dose of synthetic cannabis during pregnancy were significantly impaired on several different memory tasks involving mazes…“There was a gap in the acquisition of the memory and the consolidation of the memory.”
The young rats whose mothers were dosed with the drug also had abnormalities in the hippocampus, the brain’s primary memory center. Specifically, they had difficulty creating new connections between neurons—the basis for forming new memories. The researchers think the differences in the hippocampus stem from changes in levels of glutamate, the brain’s main excitatory neurochemical involved in learning and memory..
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How Smoking CANNABIS for a Month Affects Your Lungs
See alsoCannabis Impact on Your LungsbyBritish Lung Foundation
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J Clin Psychiatry 2018;79(6):17m11977m 10.4088/JCP.17m11977 © Copyright 2018 Physicians Postgraduate Press, Inc.
Objective: Associations between adolescent cannabis use and poor neurocognitive functioning have been reported from cross-sectional studies that cannot determine causality. Prospective designs can assess whether extended cannabis abstinence has a beneficial effect on cognition.
Conclusions: This study suggests that cannabis abstinence is associated with improvements in verbal learning that appear to occur largely in the first week following last use. Future studies are needed to determine whether the improvement in cognition with abstinence is associated with improvement in academic and other functional outcomes.
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October 2018
Marijuana use causes more long-term damage to teen brains than alcohol use, according to a new study entitled “A Population-Based Analysis of the Relationship Between Substance Use and Adolescent Cognitive Development.”
The study – completed by researchers at the University of Montreal – followed 3,800 Montreal teens over the course of four years. As part of the study, teen participants were questioned about their marijuana and alcohol use, and took computer-based cognitive tests.
They found that marijuana had more of an effect on the teens’ skills, memory and behavior than alcohol… Even after students reported stopping marijuana, their cognition did not improve.
“Cannabis causes cognitive impairment and delayed cognitive development in adolescents," Patricia Conrad, the lead author and professor of psychiatry at the University of Montreal, told NBC News. “This study focuses on the neuropsychological effects of cannabis. We think it’s important because it is linked to how someone functions in life.”
The findings were published in the American Journal of Psychiatry.