A recent analysis of more than 500,000 Canadian mothers and their children revealed a 50% increase in the risk of autism in kids whose mothers had used marijuana while pregnant, according to a report published Monday in Nature Medicine.
Daniel Corsi, the study's lead author and adjunct professor at the University of Ottawa, and his colleagues parsed data from all Ontario births occurring from 2007 to 2012.
The 503,065 children analyzed — 3,148 of whom had mothers that had used cannabis while pregnant — were followed for an average of seven years. Exactly 7,125 were diagnosed with varying levels of autism.
Researchers found that the rate of autism diagnoses among children with in utero cannabis exposure was 2.2%. Of those whose mothers did not use the drug during pregnancy, only 1.4% were diagnosed with autism.
"Cannabis is not a benign drug and any use during pregnancy should be discouraged," Corsi said. "We know that cannabinoids can cross placental tissue and enter the fetal bloodstream. There are cannabinoid receptors present in the developing fetus and exposure to cannabis may impact the wiring of the developing brain."
After researchers accounted for factors that might distort the results, they found that the risk for autism increased by 50% when mothers used cannabis while pregnant.
Ziva Cooper, interim director at the UCLA Cannabis Research Initiative, said that while the findings give some clues that "exposure to cannabis" during pregnancy "is associated with autism," there are "many questions" that still remain.
Although Cooper was not involved in the new study, she noted in an email that the women who participated were asked to self-report cannabis use and were only asked about their use of the drug once early in their pregnancy.
Nevertheless, she concluded that "these are important findings given the increase of cannabis use in pregnant women."