How Smoking Weed While Pregnant Can Create More Anxious Children

Cannabis use while pregnant may contribute to increased anxiety, hyperactivity and even aggression in children later in life, suggests a new study by researchers at New York City’s Mount Sinai hospital.

In a paper published with the Proceedings of the National Academy of Sciences journal, a possible correlation has been found between cannabis use by pregnant women and these behavioral issues in children. The research was part of a wider study examining how stress during pregnancy can impact childhood development.

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

The research involved a subset of 322 mother-child pairs from the larger study, including 71 women who reported using cannabis during pregnancy. All of the women were invited to enroll in the study during their second trimesters and to participate with their children in follow-up assessments up to four years after birth.

What they found was that cannabis use during pregnancy was associated with higher levels of stress, anxiety, aggression and hyperactivity in the children while they were young. These children were found to have higher levels of a stress hormone called cortisol in hair samples compared to children born to nonusers, and young girls born to women who used cannabis while pregnant showed higher levels of aggression in particular.

A possible genetic explanation was also identified when examining the placentas of those who used cannabis while pregnant. In these children, they detected reduced expression of several genes associated with immune system function and the differences could be directly correlated with future anxiety.

As cannabis becomes more available in the United States, its adverse side effects on adults and children have come under increasing scrutiny from researchers. Other studies have established that young people who use cannabis are at increased risk of suffering a heart attack earlier in life and that using it as a vape product can stunt their brain development.

Cannabis has been frequently marketed as a safe substance to use, but one of the study's co-authors, Dr. Yasmin Hurd, told NBC News that it is important to know the risks of its use.

“It’s not that I think that cannabis is a horrible thing,” she said. “But it is a drug that we need to make sure we understand which individuals may be more vulnerable.”