Cannabis Use During Pregnancy Linked To Increased Risk of Autism in Children
A new study has found that children born to mothers who reported using cannabis during pregnancy were at about a 50 percent greater risk of developing autism.
Published in Nature Medicine this week, the study presents an analysis of data gathered from around half a million live births in Ontario between 2007 and 2012. The team of researchers began compiling autism diagnoses, and followed up with the research subjects till 2017. The results suggested that 2.2 percent of children born to mothers who reported cannabis use during pregnancy developed autism, as compared to 1.4 percent of those born to mothers, who did not.
In order to keep the findings consistent, and minimize any bias caused by other external factors, the researchers compared 2,364 mothers who used cannabis to 170,671, who did not — but both of these sets of mothers had similar characteristics, such as age, education, health conditions, and socio-economic status. “Children with prenatal cannabis exposure had an increase of 50 percent in the risk of an autism diagnosis over the study period,” the paper states, adding: “also, children with prenatal cannabis exposure appeared to have some increased risk for developing intellectual disabilities, learning disorders and ADHD compared to unexposed children. However, these associations were smaller in magnitude.”
“There is an important parallel with alcohol use. Now the universal recommendation is no alcohol use in pregnancy and I think a similar recommendation should be made for no cannabis use in pregnancy,” Dr. Daniel Corsi, an epidemiologist at Ottawa Hospital Research Institute, and a co-author of the study, told The Guardian. He added that this is especially important now, as countries are beginning to legalize cannabis use.
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In fact, a small study published this January showed that pregnant women are using marijuana to avoid medications like anti-nausea pills, anti-psychotic medications, and opioids, which they believe are more harmful for their babies. Reportedly, 1 in 20 women in the US reported using marijuana while pregnant in 2017 — double the rate in 2002. “It helps with different conditions that they may have or for nausea and vomiting in pregnancy. Some people [said] they use [cannabis] for sleep or for stress reduction. Still others use it recreationally; it’s just part of their routine,” Dr. Darine El-Chaâr, a maternal fetal medicine specialist and clinical investigator at Ottawa Hospital Research Institute in Canada, who was one of the authors of the study, told CNN.
Previous studies have also reported links between the use of marijuana during pregnancy to low birth weight, impulsivity, attention issues, and other cognitive and behavioral issues in children. One study had, in fact, also found that smoking marijuana is associated with a 2.3 times greater risk of stillbirth. “Based on that, I’m not too surprised by these findings. Fetal brain development occurs throughout all gestational ages,” El-Chaâr added. “The finding of increased rates of autism in the offspring of mothers who used cannabis in pregnancy is not surprising given the evidence from animal studies showing how it can disrupt brain development,” Sir Robin Murray, a professor of psychiatric research at King’s College London, who was not involved in the study, said, calling it a “useful warning.”
However, the study suffers from some limitations — it didn’t study the impact of either different doses, or varied frequencies, of cannabis use. Experts also believe that since the data analyzed by the researchers was based on self-reported cannabis use, occasional use may not have been captured. Nonetheless, the study has demonstrated an association between cannabis use during pregnancy and autism, which could pave the path for further studies on the subject to determine causality, and the role genetics plays in this association.
“In the past, we haven’t had good data on the effect of cannabis on pregnancies. This is one of the largest studies on this topic to date. We hope our findings will help women and their healthcare providers make informed decisions,” Dr. Corsi concluded.