Investigating Links Between Prenatal Cannabis Exposure and Brain Development Using Magnetic Resonance Imaging Techniques: A Narrative Review

Understanding the impact of prenatal cannabis exposure (PCE) on brain development is increasingly important given rising cannabis use during pregnancy. Many existing reviews on this topic are more than 5 years old and may not reflect recent social shifts that could impact cannabis use during pregnancy; they also have not utilized the recently available large longitudinal datasets for more robust and population-representative investigations. In this narrative review, we aim to provide an updated and expanded examination of the associations between PCE and magnetic resonance imaging (MRI)-based brain outcomes from in utero development to adolescence. We included studies published after 2019 that used at least one of the following measures: structural MRI, diffusion-weighted imaging, resting-state fMRI, and/or task-based fMRI. Across 9 studies that met criteria, 1 study focused on MRI outcomes in utero, 2 in infancy, and 6 in early adolescence, and only 3 studies included MRI and behavior outcomes. PCE was linked to differences in frontal, parietal, and temporal areas, spanning from in utero to adolescence across multiple MRI modalities. However, in the current state of the literature, detecting a consistent trend on PCE's impact on MRI findings was not possible. Furthermore, we found several divergences in study design: varying approaches to assessment (e.g., self-report vs. urine toxicology); difficulties in accounting for prenatal exposure to multiple substances; limited information on timing, frequency, potency, or mode of consumption; and the influence of parental or postnatal factors. Future research should implement designs that can rigorously capture the abovementioned elements to permit replication and eventual meta-analyses on this critical topic.