The Effect of Prenatal Marijuana Exposure on White Matter Microstructure and Cortical Morphology during Late Childhood

BACKGROUND AND PURPOSE: Marijuana consumption by pregnant women has been steadily increasing during the past decades. Even though many pregnant women perceive marijuana consumption as safe during pregnancy, it has been previously linked to poor maternal and neonatal outcomes. The specific long-lasting neurodevelopmental alterations caused by prenatal marijuana exposure in children are still underexplored. Thus, this study aimed to determine the effect of prenatal marijuana exposure on brain neurodevelopment in late childhood.

MATERIALS AND METHODS: This cross-sectional study investigated the relationship between prenatal marijuana exposure and neuroimaging markers of brain health. Data were obtained from the Adolescent Brain Cognitive Development study, a large, demographically diverse, multicenter cohort. The study included 1085 children, 418 of whom were prenatally exposed to marijuana and 667 matched controls with no prenatal exposure, with a mean age of 9.9 (SD, 0.6) years in both groups.

RESULTS: We found that prenatal exposure to marijuana is associated with brain alterations in white matter tracts and cortical regions essential for goal-directed behaviors, including motivation, cognitive skills for achieving specific objectives, and emotional processing. Direct group comparisons revealed significantly reduced WM integrity in prenatally exposed children, with an overall reduction in fractional anisotropy and neurite density and higher mean diffusivity and radial diffusivity. Furthermore, mixed linear model regressions revealed that prenatal marijuana exposure was significantly associated with decreased WM microstructure, predominantly in the superior corticostriate tract and corticostriate projections via the external capsule to the superior parietal and frontal cortices and with reduced cortical surface area in the left hemisphere parahippocampal and right hemisphere postcentral gyri.

CONCLUSIONS: Overall, our findings suggest that prenatal exposure to marijuana may result in long-lasting alterations in children’s brain neurodevelopment. These alterations may impair critical skills needed as children grow into adolescence.