Pot vs. pregnancy

Children whose mothers used marijuana during pregnancy have higher levels of anxiety, hyperactivity, and aggression, according to a recent study of the effects of the drug on child development. The research, published in the Proceedings of the National Academy of Science in November, adds to a body of research showing adverse outcomes for children exposed to marijuana in utero.

“Many people think that since cannabis has been around for a long time that we know everything about this drug,” said study co-author Yasmin Hurd, director of the Addiction Institute at Mount Sinai in New York City. “That is unfortunately not true.”

Hurd and her colleagues at the Icahn School of Medicine examined 322 children born at Mount Sinai Hospital or New York-Presbyterian Queens. Starting when the children were 3 years old, researchers evaluated their stress hormone levels using hair samples, heart function via electrocardiogram recordings, and behavioral and emotional functioning via surveys administered to the children’s parents. The evaluations continued until age 6. The study found higher rates of the stress hormone cortisol in children of mothers who used marijuana during pregnancy, along with increased anxiety, hyperactivity, and aggression.

The researchers also analyzed placenta from some of the mothers after they gave birth. They found that marijuana use decreased the expression of immunity-activating genes. The cannabinoid tetrahydrocannabinol (THC) is known to cause immunosuppression, and the researchers believe that phenomenon may lead to the observed spike in stress and anxiety in early childhood.

The human body produces molecules called endocannabinoids that regulate many bodily functions, including mood, memory, sleep, and pain. When a pregnant women smokes marijuana, THC overwhelms receptors within the endocannabinoid system, producing a desired short-term high.

Study co-author Yoko Nomura, a professor at Queens College, City University of New York, explained that while a pregnant woman may use marijuana to relieve stress or anxiety, the disruption of her baby’s endocannabinoid system could permanently alter regulation of the baby’s bodily functions. “The mother is looking for instant relief, without knowing there is a long-term consequence,” said Nomura.

The study controlled for risk factors that could contribute to a child’s development of behavioral issues, such as household cigarette smoking and parental anxiety. But Nomura noted that some factors are impossible to control for. For example, cannabis smokers may have a different lifestyle than abstinent mothers. Nomura also pointed out that the study’s small sample size makes it difficult to draw sweeping conclusions.

An estimated 7 percent of pregnant women in the United States smoke marijuana, according to a national survey conducted in 2016. Previous studies suggest maternal cannabis use is associated with other adverse outcomes for children, including reduced birth weights and shorter memory and attention spans into adolescence.

Still, little is understood about the biological processes that explain these outcomes. Nomura believes the immunosuppression evident in the placenta of marijuana smokers is a strong indicator of a biological mechanism, but she said more research is needed: “We really should be humble to know that there is so much more to know.”

Given the uncertainties, both Nomura and Hurd caution against using cannabis while pregnant. Nomura believes the best way to steer pregnant women away from marijuana use is not through scare tactics but through encouragement to make healthier decisions. A small change, such as walking for five minutes a day, can make a huge difference. When family members also make lifestyle changes to support the pregnant woman, Nomura said, it bolsters her ability to keep moving in a healthy direction.