Researchers discuss the potential biological pathways through which prenatal cannabis exposure could contribute to behavioral issues in the long term.
Scientists are investigating the effects of cannabis on long-term brain development when individuals were exposed to it before birth. Previous research by WashU scientists Sarah Paul and David Baranger in the Behavioral Research and Imaging Neurogenetics (BRAIN) lab, led by Ryan Bogdan, found links between prenatal cannabis exposure and potential mental health conditions during childhood and adolescence, but the specific biological mechanisms were unclear.
In a recent study published in Nature Mental Health, Bogdan, Dean’s Distinguished Professor of Psychological & Brain Sciences at Washington University in St. Louis, and Postdoctoral Fellow Baranger, delve into some of these potential mechanisms, outlining the intermediate biological processes that may contribute to the development of behavioral issues following prenatal cannabis exposure.
“We have observed indications that cannabis exposure could affect the developing brain, which aligns with its associations with mental health issues,” explained Baranger.
Unraveling the long-term consequences of cannabis exposure during pregnancy is a complex task. Numerous factors can influence mental health and behavior. For instance, if an individual was exposed to cannabis before birth and later develops attention deficit disorder as a teenager, it becomes challenging to differentiate whether this is an inherited trait, influenced by environmental factors, or impacted by prenatal cannabis exposure. It’s possible that all three factors contribute to eventual psychological problems. Additionally, the rising prevalence of cannabis use, particularly among pregnant women where usage has increased from 3 to 7 percent between 2002 and 2017, adds another layer of complexity.
Researchers employed statistical methods to address some of these confounding variables and identify potential biological links between prenatal cannabis exposure and various adolescent behaviors.
While causation cannot be definitively established, “we can assess the likelihood of causation, and pinpointing potential biological markers associated with cannabis exposure and subsequent mental health issues indicates plausibility,” Bogdan commented on the study findings.
The researchers utilized data from the Adolescent Brain and Cognitive Development (ABCD) Study, a large-scale research initiative encompassing nearly 12,000 children nationwide. As part of this study, information on maternal substance use prior to childbirth and neuroimaging data at ages 9-10 and 11-12 was collected. Out of the participants, 370 children were exposed to cannabis before their mother’s knowledge of pregnancy, while 195 were exposed both before and after pregnancy recognition.
The researchers examined various neuroimaging metrics crucial for brain development, such as brain thickness, surface area, and water diffusion in and out of cells. The brain patterns observed in children exposed to cannabis prenatally were suggestive of potential reductions in neuroinflammation.
“There is a possibility that we are observing an anti-inflammatory impact of cannabis, contributing to differences in brain pruning during neurodevelopment,” Bogdan noted.
While cannabis is often praised for its anti-inflammatory properties, excessive reduction of inflammation at the wrong time could influence brain pruning and maturation negatively.
Another hypothesis suggests that cannabis exposure could lead to accelerated aging. However, identifying definitive biological evidence linking mental health conditions to early cannabis exposure may be elusive.
It may not solely be about brain pruning or cannabis use itself; combustion byproducts from smoking cannabis could potentially trigger accelerated aging and subsequent cognitive effects, as indicated by Bogdan.
Alternatively, sociological factors may play a role in this complex interplay.
Establishing a direct connection proving the negative effects of prenatal cannabis exposure during adolescence through retrospective studies poses a significant challenge. Baranger highlights that a major limitation of this dataset is its retrospective nature; mothers reported their cannabis use a decade earlier, underscoring the need for prospective, longitudinal studies offering more recent, accurate, and detailed information on cannabis use during pregnancy.
“Future studies can potentially provide more insights into these questions,” Baranger emphasized.
In the interim, the study findings underscore the importance of consulting a healthcare provider about choices and alternatives if considering cannabis use during pregnancy, according to Baranger.
