Canadian Geospatial Analysis Finds Association Between Cannabis Use and Major Congenital Anomalies

In Canada, roughly two thirds of pregnant women presenting to cannabis dispensaries are recommended cannabis products to treat pregnancy-related nausea, despite the fact that animal studies have suggested a relationship between cannabis and serious birth defects. Canada presents an ideal opportunity to study these relationships in human populations given its national birth registry on congenital defects and nationwide survey data on cannabis use. Using data obtained between 1998 and 2009, the authors employed geospatial regression analyses to explore the association between prenatal cannabis exposure and teratogenicity.

• Mapping showed cannabis use was more common in the northern Territories of Canada.
• All congenital anomalies, cardiovascular defects, orofacial clefts, Downs syndrome, and gastroschisis were found to be more common in the northern Territories of Canada, compared with the Provinces, (odds ratio, 1.16) and rose as a function of cannabis exposure.
• By geospatial analysis model, cannabis was significant both alone as a main effect and in all its first and second-order interactions with both tobacco and opioids.

Comments: This sophisticated geospatial analysis in Canada suggests a distinct association between cannabis use and major congenital anomalies. Although potential confounding may contribute to this association, these findings—taken with cellular and animal studies that similarly suggest an association—should be explored further.

Jeanette M. Tetrault, MD

Reference: Reece AS, Hulse GK. Canadian cannabis consumption and patterns of congenital anomalies: an ecological geospatial analysis. J Addict Med. 2020;14(5):e195-e210.