Canadian Study Links Prenatal Cannabis Use and Autism

A new cohort study published in Nature Medicine has found a correlation between prenatal cannabis use and autism spectrum disorder (ASD). The cohort study involved over 500,000 Canadian births, and found that children with mothers who reported cannabis use had a 50% increase in risk of an autism diagnosis, as well as a less significant increases in risk of developing intellectual disabilities or ADHD (11-22%).


This study is further evidence to support the position that women who are pregnant or plan to become pregnant should avoid using cannabis products that contain THC.


Previous research has demonstrated that cannabinoids like THC can cross the placenta and enter fetal bloodstreams. Animal data has also found that the fetal endocannabinoid type 1 receptor (CB1)—the cannabinoid receptor found in the highest concentrations in the central nervous system—is already expressed at what would be the equivalent of 5-6 weeks of gestation in humans. More importantly, these animal studies have long suggested that cannabis, particularly tetrahydrocannabinol (THC), can harm developing brains in utero and lead to cognitive impairment.


While the findings of the new study are significant, the authors note several limitations. Perhaps most crucially, the authors state that cannabis use by the recent mothers was self-reported. As there continues to be a stigma about the use of cannabis by pregnant women, there is a fear that the data may not be entirely accurate and that rates of usage and frequency of use in the study may have been significantly underreported. This would have had the effect of augmenting the apparent correlation between prenatal cannabis use and ASD.


More studies are certainly needed to better understand how cannabis affects fetuses, but at this time it remains wise for women who are pregnant or plan to become pregnant to avoid using cannabis products that contain THC.


To read the full study, click here.

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