Children whose mothers used cannabis after the fifth or sixth week of pregnancy may be more likely to develop mental health problems in early adolescence, a new study has found.
An analysis of data from over 10,000 children aged 11 and 12 found that exposure to cannabis in utero was associated with a higher risk of developing disorders such as ADHD, aggressive behavior, conduct disorder and behavior that violates the rules, according to The report published in JAMA Pediatrics.
“The take-home message from this study is that there is evidence to be cautious about cannabis use during pregnancy,” said study first author David Baranger, a postdoctoral researcher at the Washington University in St. Louis.
The new study is an association and cannot prove that cannabis is the cause of mental health problems, Baranger said.
However, the results match previous research on the same children, who participated in the current study. Cognitive development of the adolescent brain (ABCD). The long-term project, which is backed by the National Institutes of Health, tracked the brain development of nearly 12,000 children via MRI scans.
The children’s brain scans “showed a hint of potential impact from cannabis,” Baranger said.
A study 2019 who examined children when they were 9 and 10 years old found the same association between prenatal cannabis and behavioral problems. It also showed that children exposed to cannabis in utero tended to have lower birth weight, lower brain volume and lower white matter volume.
Although still a small percentage, the number of women using cannabis during pregnancy increases. In 2018, 4.7% of pregnant women reported using cannabis and 5.4% in 2019, according to a government inquiry.
For pregnant women who rely on marijuana for nausea relief, Baranger advised talking to their healthcare provider.
Baranger and his colleagues analyzed data from 10,631 children who participated in the NIH Brain Study. The researchers compared three groups of children:
- those whose mother did not use cannabis during pregnancy,
- those whose mothers used cannabis but stopped when they found out they were pregnant,
- and those whose mothers continued to use cannabis after learning they were pregnant.
The impact of cannabis use was observed in the middle of the first trimester. Using it earlier in pregnancy — before mothers find out they were pregnant — doesn’t seem to impact the risk of children developing behavioral problems, Baranger said. He suspects it’s because cannabinoid receptors haven’t yet developed in the fetal brain.
The new research indicates that the problems discovered in the previous study persist in 12-year-old children, said Staci Gruber, associate professor of psychiatry at Harvard Medical School, director of the Marijuana Investigations for Neuroscientific Discovery (MIND) program and Cognitive and Neuroimaging Core at Harvard’s McLean Hospital.
It’s not hard to imagine why cannabis might appeal to some women, Gruber said. “You can understand why they might turn to something like this,” she added. “They might think it’s natural and won’t hurt anything.”
But Gruber said there are many examples of natural substances that can harm people.
The big limitation of the study is that the dataset the researchers used didn’t contain information on how often the women used cannabis, or what form they used, Gruber said.
Learn more about cannabis use and children
Cannabis use during pregnancy appears to increase the risk of children having long-term behavioral and cognitive problems, said Dr. Nora Volkow, director of the National Institute on Drug Abuse at the National Institutes of Health.
“This association is now shown to persist into early adolescence and in the future may lead to other psychopathologies,” she said.
Cannabis use is “really undesirable because it’s a drug that crosses the placenta and enters the fetus,” Volkow said. “At first, cannabinoid receptors are widely expressed in the brain.”
Cannabinoids are important in orchestrating some of the processes that help guide neurons from the center of the developing brain to the distant points that will become the cortex, Volkow said.
“If the person is taking marijuana, it’s going to artificially stimulate the receptors, which could lead to deviations from the very specifically orchestrated process,” Volkow said.
How to Treat Nausea During Pregnancy
There are prescription medications available to treat nausea during pregnancy. For those who want to avoid taking medication, there are behavioral interventions, Volkow said.
Several are described in an American College of Obstetricians and Gynecologists publication.
Recommendations for nausea during pregnancy include:
- Eat small, frequent meals every 1-2 hours to avoid a full stomach.
- Avoid spicy or fatty foods.
- Eliminate extra iron.
- Substitute folic acid for prenatal vitamins containing iron.
- Eat bland or dry foods, high-protein snacks, and crackers in the morning before getting up.