New study shows exposure to marijuana in utero may have lasting mental health effects

A new study published this week by the Journal of the American Medical Association (JAMA) showed there may be a link between the use of marijuana while a child is in utero and the child’s mental health later in life.

The study, which focused on nearly 10,000 of the 12,000 children who have been followed by researchers from birth to adolescence as part of the Adolescent Brain Cognitive Development study, showed that those whose mothers utilized cannabis after the fifth or sixth week of pregnancy displayed a greater likelihood of developing mental health issues including ADHD, conduct disorder, rule-breaking behaviors and aggression. 

After studying three groups of people – those who never used cannabis while pregnant, those who used it but stopped when they found out they were pregnant, and those who continued to use it after finding out they were pregnant – researchers found the group whose mothers used cannabis after finding out they were pregnant showed similar brain scan data.

The research team was able to determine that using cannabis early in pregnancy does not seem to have an effect on the brain. They believe this is because the cannabinoid receptors in the human brain do not develop until later.

While the study does appear to show a strong link between in utero marijuana use and mental health, researchers were careful to point out that the study is an association, and cannot prove definitively that the patterns are attributed to marijuana use.

“The take-home message from this study is that there is some evidence that one should be cautious about using cannabis during pregnancy,” said David Baranger, a researcher on the project, to NBC News.