Researchers from The Ottawa Hospital in Ontario, Canada, have found that children born to mothers who used cannabis while pregnant are more likely to have autism than children born to mothers who did not use the substance while pregnant. Given the legalization of recreational cannabis in many jurisdictions, the study raises concerns over the potential adverse outcomes of prenatal exposure.
For the study, the researchers reviewed medical records of over 500,000 births in Ontario between April 2007 and March 2012. In total, they reported that 0.6% of the mothers studied used cannabis during pregnancy. Meanwhile, 1.4% of children studied were diagnosed with autism. This figure increased to 2.2% if their mother had smoked cannabis during pregnancy.
When controlling for various other factors, the researchers found that 4 in 1000 children born to mothers who used cannabis during pregnancy had autism. In contrast, the same figure was just 2.42 out of 1000 for unexposed children. The researchers also found a link between intellectual disability and learning disorders in children whose mothers used cannabis during pregnancy.
Although interesting findings, especially given the large sample size, the researchers warn that their study does not prove that cannabis use during pregnancy causes autism. Rather, they say that their findings suggest an association between the factors. This comes especially as how much cannabis was consumed, how often, and at what stage of pregnancy was not recorded.
Nevertheless, the findings may be significant enough to encourage pregnant women to exercise caution when using cannabis. This may especially be the case given recent findings showing that women who consume cannabis while pregnant have a higher risk of premature birth, and delivering babies with low birth weight.
"We know so little about how cannabis affects pregnant women and their babies," says Dr. Mark Walker, one of the study's authors. "Parents-to-be should inform themselves of the possible risks, and we hope studies like ours can help."