The study, designed to assess what exposure to marijuana in utero could mean for child development and mental health, focused on a few measurements in kids, including behavior, hormone levels, and heart rate variability. Particularly, the researchers note that they were looking for anxiety-related issues. The study examined more than 300 parent-child pairs, split into those who used marijuana during pregnancy and those who didn’t. The researchers took hair samples from the kids to test for hormone levels, observed their behavior using a standard assessment, measured their heart rates, and took samples of the placenta. They found that kids exposed to weed in the womb had higher average levels of cortisol, often referred to as the “stress hormone.” Cortisol plays an important role in the body, but a high level maintained over time is associated with long-term stress and can have negative effects. The researchers also found significant differences between the two groups in a type of heart rate variability that can also be associated with stress. In addition, kids exposed to cannabis during pregnancy had significantly higher than average levels of aggression, anxiety, and hyperactivity compared to the non-marijuana group. However, this study is not nearly enough to say that smoking weed during pregnancy causes any of these conditions or behaviors. The researchers speculated that the differences could stem from differences in gene expression in the placenta. They found that some immune-related genes were expressed differently between the two groups, in ways that could potentially account for the higher anxiety levels observed in kids exposed to marijuana during fetal development. This indicates that using marijuana during pregnancy could lead to other long-term impacts on these kids too, Yasmin Hurd, Ph.D., a neuroscientist at Mount Sinai Hospital in New York and one of the study’s authors, told Fatherly. This study isn’t the only one to find an association between marijuana use during pregnancy and later anxiety in children. A new study also found such a relationship for children aged 11 and 12, as well as a link between marijuana use and other psychopathology, including aggressive behavior, ADHD problems, and psychoticlike experiences. The Centers for Disease Control and Prevention recommends against smoking weed during pregnancy, and studies such as these show that pre-natal exposure could be detrimental to kids. But, especially since weed is just now becoming more widely used, more studies are needed to fully understand the relationship between marijuana and child development. Part of the reason for the overall shortage of studies on marijuana during pregnancy is that marijuana is still illegal at the federal level, and hardly any states had legalized weed until recently. But as legalization comes in rapid succession to many states, people are encountering weed in their lives a whole lot more — and weed use among pregnant people has also increased recently. “Legalization of cannabis has made many people think that it is without any health risk,” Hurd says. But smoking weed during pregnancy is not innocuous and likely comes with risks that are still unknown.
