November 15, 2021

By Lida Tunesi

powder in paper in hands
Credit: Getty Images

As cannabis becomes more widely legalized, scientists are working to elucidate its effects on human health. A new study addresses the question of whether the drug is safe to use during pregnancy.

The paper, published in Proceedings of the National Academy of Sciences, shows a correlation between maternal cannabis use and increased anxiety in young children. The researchers also saw reduced expression of genes related to the immune system in the mothers’ placenta.

Professor Yoko Nomura (GC/Queens, Psychology) was co-first author on the paper, written in collaboration with researchers from the Icahn School of Medicine, where Nomura is also a lecturer.

“The endocannabinoid system in the brain is known to modulate the level of stress,” Nomura said. “Early exposure appears to overwhelm the system, preventing it from functioning as well as it would otherwise.”

Nomura and her collaborators looked at data on 322 pairs of children between the ages of about three and six and their mothers in New York City, originally gathered as part of a larger Stress in Pregnancy project started in 2009.

The children whose mothers used cannabis showed higher anxiety, aggression, and hyperactivity than children of mothers who did not partake, and samples of the kids’ hair had increased levels of the stress hormone cortisol. The same kids had a reduced high-frequency component of their heart rate variability, a trait associated with several anxiety-related disorders in young kids and adults, the authors wrote.

When the researchers saw lowered expression of immune-related genes in the mothers’ placentas, they analyzed the genes and found that those gene networks correlated with anxiety problems and hyperactivity. This means that the effects of cannabis on immune response genes in the placenta might be the link to the young children’s altered traits.

“Just like smoking and alcohol intake, pregnant mothers would do best to avoid using cannabis,” Nomura said. “The truth is that we really do not know the extent of its influence across the life span yet. One should not use it as a method to alleviate morning sickness.”

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