Prenatal Marijuana Exposure Linked to Brain White Matter Changes in 10-Year-Olds

Prenatally exposed children (n=418) showed significantly reduced white matter integrity (lower fractional anisotropy and neurite density, higher mean and radial diffusivity) compared to 667 matched controls. The most affected tracts were the superior corticostriate tract and projections to frontal and parietal cortices. Cortical surface area was reduced in the left parahippocampal and right postcentral gyri.

Cross-sectional neuroimaging study using ABCD Study data. 1,085 children (mean age 9.9 years): 418 prenatally exposed to marijuana, 667 matched controls with no prenatal exposure. Diffusion MRI assessed white matter microstructure. Mixed linear models accounted for multiple covariates.

This is one of the largest neuroimaging studies of prenatal marijuana exposure to date. The finding that white matter tracts connecting motivation and goal-directed behavior centers are specifically affected suggests a biological pathway through which prenatal cannabis exposure could impair executive function as children enter adolescence.

The corticostriate tracts affected in this study connect prefrontal cortex to reward/motivation centers. As these children enter adolescence -- when executive function demands increase dramatically -- these structural differences could become functionally consequential, potentially affecting academic performance, decision-making, and risk-taking behaviors.

Cross-sectional design cannot determine whether prenatal marijuana exposure caused the brain differences. Prenatal exposure was typically assessed by maternal report and may be underreported. Other prenatal exposures (tobacco, alcohol, stress) may confound results despite statistical control.