In a recent mouse study, researchers found that heavy cannabis use during pregnancy negatively affects fetal brain development and that these effects persist into adulthood. The research was published in Molecular Psychiatry.
“Since cannabis legalization is relatively recent, we don’t yet have long-term human data on newer THC products. Our findings offer an early glimpse of possible outcomes a decade or two down the line,” said senior study author Mallar Chakravarty, Full Professor in the Department of Psychiatry at McGill University, Canada, in a press release.
For the study, researchers simulated daily exposure to cannabis equivalent to one or two joints containing over 10% THC during a period similar to the first trimester of human pregnancy. They used magnetic resonance imaging at nine time points alongside behavioral assays and electron microscopy to map the effects of THC on the mice's brains over time.
Ultimately, they found that heavy THC use influenced developmental changes across three life stages: late pregnancy, early life, and adolescence to adulthood. In late pregnancy.
As for late pregnancy, THC-exposed embryos were found to have smaller bodies and larger brain ventricles, signaling abnormal brain development. Newborns tended to gain weight faster while their brains developed more slowly. These smaller brain volumes persisted between adolescence and adulthood, particularly in female mice, who also displayed more anxiety-like behaviors.
“The good news is that many of these developmental delays are subtle and could likely be offset with a supportive environment,” said Chakravarty.
Until now, most studies on humans underlying words of caution from public health agencies around cannabis use during pregnancy have been observational in nature. The current findings offer biological evidence showing how heavy cannabis use can disrupt neurodevelopment.
"Our results suggest prenatal THC exposure has a sustained sex-dependent impact on neurodevelopment that may persist into early adulthood," concluded the researchers in their study.
A follow-up study will look into whether other modes of cannabis consumption, like edibles, vaping, and CBD products, affect the brain differently.
Sources: EurekAlert, Molecular Psychiatry