The risk of autism may be greater in children born to women who used marijuana during pregnancy, a new study suggests.
In an analysis of data from more than 500,000 Canadian mothers and their children, researchers found a 50 percent increase in the risk of autism spectrum disease in children whose mothers had used cannabis while pregnant, according to the report, published Monday in Nature Medicine.
“Cannabis is not a benign drug and use during pregnancy should be discouraged,” said the study’s lead author, Daniel Corsi, an adjunct professor at the University of Ottawa and a researcher at the Children̵
“We know that cannabinoids can cross placental tissue and enter the fetal bloodstream,” Corsi said. “There are cannabinoid receptors in the developing fetus and exposure to cannabis can affect the conduction in the developing brain.”
While it is known that substance use in pregnant women can affect fetal neurodevelopment, the question of whether cannabis use is a risk factor for autism has not been thoroughly investigated, said Daniele Fallin, director of the Wendy King Center for Autism and Developmental Disabilities at Johns Hopkins Bloomberg School of Public Health. said in an email.
Fallin, who was not involved in the new research, said the observational study could not prove that pregnant women using cannabis cause autism. “This is an interesting first step, but much more work is needed to involve the mater’s cannabis use specifically at autism risk,” she added.
To take a closer look at the possible neurodevelopmental effects of cannabis on developing fetuses, Corsi and his colleagues reviewed data from all Ontario births that occurred from 2007 to 2012, which was before the drug was legalized in Canada. Their final analysis included 503,065 children, of whom 3,148 had mothers who used cannabis while pregnant.
The children were followed for an average of seven years, during which 7,125 were diagnosed with autism spectrum disorder. The proportion of autism diagnoses among children with exposure to utero-cannabis was 2.2 percent, compared with 1.4 percent in those whose mothers did not use the drug during pregnancy.
When the researchers reported factors that could skew their results, they found that the risk of autism increased by 50 percent when mothers used cannabis during pregnancy.
“This finding provides some clues that exposure to cannabis in utero is associated with autism, but many questions remain,” said Ziva Cooper, interim director of the UCLA Cannabis Research Initiative, in an email. She found that the women in the study were asked to self-report cannabis use and only asked about it at some point early in their pregnancy.
Still, “these are important findings given the increase in cannabis use among pregnant women,” said Cooper, who was not involved in the new research.
Last summer, research from Kaiser Permanente Northern California found that cannabis use is increasing among pregnant women in the United States. The proportion of women who used the drug while pregnant increased from 1.9 percent in 2009 to 3.4 percent in 2017.
Canada legalized the use of recreational marijuana in 2018, a change that is likely to lead to an increase in people using the drug, says Dr. Richard Miller, professor of pharmacology at Northwestern University’s Feinberg School of Medicine and author of “Drugged: The Science and Culture Behind Psychotropic Drugs.” The new study raises an important question: Will it be safe to use pregnant women?
“The most important finding – a very recent one – is that the number who can get autism increased by a significant amount,” Miller said. “The message of bringing home this paper, which I think is good enough, is that women really should think very carefully about this.”
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