Children exposed to cannabis before birth showed subtle changes in brain white matter tracts involved in emotion and memory | Research

The takeaway

Among 11,530 children in the ABCD Study, prenatal cannabis exposure was associated with lower white matter integrity in the fornix, a brain pathway critical for emotion and memory processing.

Developmental neuroscientists studying prenatal exposures; OB-GYN providers counseling patients about cannabis use during pregnancy.

11,530 children; fornix white matter integrity reduced with prenatal exposure

What the researchers found

Prenatal cannabis exposure was associated with lower fractional anisotropy (a measure of white matter integrity) in the right and left fornix. These effects remained significant after adjusting for covariates, multiple comparisons, overall white matter, and a quality-control subset. The effects were small but reliable.

Why it matters

This is one of the largest neuroimaging studies of prenatal cannabis exposure, drawing from a nationally representative sample. The fornix is rich in cannabinoid receptors and plays a key role in the hippocampal memory circuit, making it biologically plausible as a target of prenatal cannabinoid exposure.

The numbers in context

11,530 children from the ABCD Study. Right fornix: beta = -0.005, p significant. Left fornix: p = 0.007. Effects survived adjustment for covariates, multiple comparisons, and quality-control subset analysis.

How the study worked

Cross-sectional analysis of 11,530 children (mean age ~10 years, 47% female) from the Adolescent Brain Cognitive Development (ABCD) Study. Linear mixed-effects models examined caregiver-reported prenatal cannabis exposure and fractional anisotropy of 10 frontolimbic white matter pathways.

What this study cannot tell us

Cross-sectional analysis of a developmental cohort. Prenatal exposure based on caregiver recall, which may be inaccurate. Small effect sizes. Cannot determine timing, dose, or frequency of prenatal exposure. Cannot rule out confounders related to maternal health or environment.

How to read the evidence

Very large nationally representative sample with robust statistical controls. Cross-sectional design and retrospective exposure assessment limit causal claims.

When this study was published

2024 study

The bigger picture

While the effects are small, they add to growing evidence that prenatal cannabis exposure leaves detectable traces on brain development. Whether these subtle structural changes translate to functional problems in emotion regulation or memory remains an important open question.

Questions still open

Do these white matter differences persist into adolescence? Do they predict measurable differences in memory or emotional functioning?

Common questions

What is the fornix?

A C-shaped bundle of nerve fibers connecting the hippocampus to other brain regions. It plays a critical role in memory formation and emotional processing and has a high density of cannabinoid receptors.

Are these brain changes harmful?

The study found structural differences but did not assess whether they cause functional problems. The effects were small, and the researchers note that future studies are needed to understand whether these changes affect behavior or cognition.

Read the original research

The First "Hit" to the Endocannabinoid System? Associations Between Prenatal Cannabis Exposure and Frontolimbic White Matter Pathways in Children.

Biological psychiatry global open science, 4(1), 11-18

View on PubMed ↗Publisher’s paper ↗

Citation

Evanski, Julia M; Zundel, Clara G; Baglot, Samantha L; Desai, Shreya; Gowatch, Leah C; Ely, Samantha L; Sadik, Nareen; Lundahl, Leslie H; Hill, Matthew N; Marusak, Hilary A. (2024). The First "Hit" to the Endocannabinoid System? Associations Between Prenatal Cannabis Exposure and Frontolimbic White Matter Pathways in Children.. Biological psychiatry global open science, 4(1), 11-18. https://doi.org/10.1016/j.bpsgos.2023.09.005