Using cannabis while pregnant can affect placenta, stress, anxiety, development in children: study

TORONTO —
Cannabis use during pregnancy has become increasingly common over the past two decades, but a study published Monday suggests that those children showed higher levels of a stress hormone, and greater anxiety, aggression, and hyperactivity.

The peer-reviewed study, published in Proceedings of the National Academy of Science (PNAS), found significant correlation between cannabis use during pregnancy and many aspects of early childhood development, the authors wrote.

“Pregnant women are being bombarded with misinformation that cannabis is of no risk, while the reality is that cannabis is more potent today than it was even a few years ago. Our findings indicate that using it during pregnancy can have long-term impact on children,” said Yasmin Hurd, Director of the Addiction Institute at Mount Sinai, and senior author of the paper, in a statement.

Led by researchers with the Icahn School of Medicine at Mount Sinai and City University of New York, 322 individuals who reported using cannabis during their pregnancy and/or while breastfeeding were tracked and the placenta collected after birth. They followed up with their children when they were around three- to six-years-old.

Researchers measured hair hormone levels, heart rate variability (HRV) at rest and during auditory startle — a test of an unconditional reflex caused by an unexpected loud sound — of the children and looked at their neurobehavioral traits as measured on the Behavioral Assessment System for Children survey.

Hair samples found higher levels of the cortisol stress hormone, along with a decrease in normalized heart rate variability. HRV typically decreases during stress and is viewed as a marker of the autonomic nervous system function and sensitivity to stress. Elevated levels of anxiety, aggression and hyperactivity were also measured in the young children, the study found.

The placenta of some of the children with behavioural assessments were processed for RNA sequencing, with scientists finding that cannabis use during pregnancy was associated with lower expression of immune-activating genes, including proinflammatory cytokines and immune cell–type markers which help protect against pathogens.

“Using gene co-expression analysis, we revealed immune-related gene networks in placenta significantly correlated with anxiety problems and hyperactivity,” the authors wrote.

“In line with previous investigations reporting greater risk for psychiatric illness in … children with prenatal cannabis exposure, the current study showed that [maternal cannabis use] is associated with increased anxiety, aggression, and hyperactivity in young children. Moreover, along with several altered psychobehavioral traits, [these] children exhibited endocrine and physiological phenotypes consistent with aberrant stress and anxiety regulation.”