Prenatal cannabis exposure following the middle of the first trimester—generally after five to six weeks of fetal development—is associated with attention, social, and behavioral problems that persist as the affected children progress into early adolescence (11 and 12 years of age), according to new research supported by the National Institute on Drug Abuse (NIDA), part of the National Institutes of Health. These conditions may put these children at a greater risk of mental health disorders and substance use in late adolescence, when youth are typically most vulnerable to these disorders and behaviors.

Published today in JAMA Pediatrics, this study analyzed data from the ongoing Adolescent Brain Cognitive Development (ABCD) Study, the largest long-term study of brain development and health in children and teens in the United States, which is supported by NIDA and nine other Institutes, Centers, and Offices of the NIH. The study was conducted by scientists at Washington University in St. Louis.

These findings add to an expanding body of research on the effects of cannabis use during pregnancy. A previous analysis using baseline data from the ABCD Study found an association between prenatal cannabis exposure and behavioral problems in these children at 9 to 10 years of age. Preclinical studies have shown that delta-9-tetrahydrocannabinol (THC), the main psychoactive substance in cannabis, can cross the placenta and potentially affect brain development.

Cannabis use among pregnant women increased from 3% in 2002 to 7% in 2017. In 2018, 4.7% of pregnant women reported cannabis use and 5.4% did in 2019, according to the National Survey on Drug Use and Health. The results of this new analysis further support caution against using cannabis during pregnancy, the authors say.

The ABCD Study tracks nearly 12,000 youth as they grow into young adults. Investigators regularly measure participants' brain structure and activity using magnetic resonance imaging (MRI), and collect psychological, environmental, and cognitive information, as well as biological samples. The ABCD Study seeks to understand the factors that influence brain, cognitive, and social-emotional development, with the ultimate goal of providing actionable information to help educators, health professionals, and policymakers improve the lives of all children, today and for generations to come.

The Adolescent Brain Cognitive Development Study and ABCD Study are registered trademarks and service marks, respectively, of the U.S. Department of Health and Human Services.