Using cannabis during pregnancy reduces the expression of immune-activating genes in the placenta, resulting in higher levels of anxiety, aggression, and hyperactivity in children by the time they reach six years of age. This is according to a new study in the Proceedings of the National Academy of Sciences, which also found impaired heart function in children born to mothers who ingested the drug while pregnant.
“We know that cannabinoid signaling plays a role in modulating stress, which is why some people use cannabis to reduce anxiety and relax,” said study author Yoko Nomura in a statement. “But our study shows that in utero exposure to cannabis has the opposite effect on children, causing them to have increased levels of anxiety, aggression, and hyperactivity compared to other children who were not exposed to cannabis during pregnancy.”
The research involved 322 mother-child pairs who took part in a long-term study into stress in pregnancy. At roughly six years of age, each child was assessed for neurobehavioral traits, with the results indicating higher levels of anxiety, aggression, and hyperactivity in those whose mothers had used cannabis while pregnant.
An analysis of the youngsters’ hair also revealed higher levels of the stress hormone cortisol in those that had been exposed to cannabis while in the womb. In addition, the researchers found that these children displayed a reduction in the high-frequency component of heart rate variability (HRV) – which refers to the change in time interval between heartbeats – at rest and when startled by loud noises.
Explaining the significance of this finding, the authors write that “low resting HRV is associated with multiple anxiety-related disorders in both young children and adults and is a risk factor for cardiovascular disease.”
A subset of the mothers involved in the study also provided samples of their placental tissue to the researchers. RNA sequencing revealed a reduction in the expression of genes associated with immune system function in the placentas of women who used cannabis during their pregnancies. Among the genes affected were those that help to ward off pathogens by regulating proinflammatory cytokines and immune cell-type markers.
Significantly, the suppression of these genes was directly correlated with anxiety levels in children. Summing up their work, the authors explain that “overall, our findings reveal a relationship between [maternal cannabis use] and immune response gene networks in the placenta as a potential mediator of risk for anxiety-related problems in early childhood.”
while noting it's a small study, expanding on this conclusion, study author Yasmin Hurd warned that “pregnant women are being bombarded with misinformation that cannabis is of no risk, while the reality is that cannabis is more potent today than it was even a few years ago. Our findings indicate that using it during pregnancy can have a long-term impact on children.”