Marijuana use during pregnancy likely to affect children's mental health: Study

A new study suggests that 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.

An analysis of data from more than 10,000 children aged 11 and 12 revealed that exposure to cannabis in utero was associated with a higher risk of developing disorders such as ADHD, aggressive behavior, conduct disorder and rule-breaking behavior, according to the report published in JAMA Pediatrics.

“The take-home message from this study is that there is some evidence that one should be cautious about using cannabis during pregnancy,” said the study’s first author, David Baranger, a postdoctoral research associate at Washington University in St. Louis.

The new study is an association and can’t prove that cannabis is the cause of the mental health problems, Baranger said.

However, the results fall in line with earlier research on the same children, who were participants in the ongoing Adolescent Brain Cognitive Development (ABCD) study. The long-term project, which is supported by the National Institutes of Health, has been tracking the brain development of nearly 12,000 children via MRI scans.

The brain scans of the children “showed a hint of a potential impact of cannabis,” Baranger said.

A 2019 study that looked at the children when they were 9 and 10 found the same association between prenatal cannabis and behavioral issues. 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 is growing. In 2018, 4.7% of pregnant women reported cannabis use and 5.4% did in 2019, according to a government survey.

For pregnant women who rely on marijuana to help with nausea, Baranger advised talking to their health care provider.