Scientists are trying to understand how cannabis exposure in utero affects long-term neurodevelopment. Previous studies by University of Washington researchers Sarah Paul and David Baranger of the Ryan Bogdan-led Behavioral Research and Imaging Neurogenetics (BRAIN) Lab found an association between prenatal cannabis exposure and potential psychiatric disorders in childhood and adolescence, but the biological mechanisms that could explain this association were unclear.
In a study published this month in the journal Nature Mental Health, Bogdan, Dean’s Distinguished Professor of Psychological and Brain Sciences at Washington University in St. Louis, and postdoctoral researcher Balanger outline some of the intermediate biological steps, or potential mechanisms, by which prenatal cannabis exposure may lead to behavioral problems later in life.
There is evidence that cannabis exposure can affect brain development, which is consistent with links to mental health.”
David Baranger, Postdoctoral Research Fellow
Unravelling the long-term effects of cannabis exposure during pregnancy is not an easy problem to solve. There are many confounding factors that affect mental health and behavior. For example, say someone was exposed to cannabis in utero and then developed attention deficit disorder as a teenager. How do we distinguish this as a genetic trait, or a trait influenced by environmental factors, or a trait due to exposure to cannabis during early development? Or maybe all three of these processes contribute to the eventual psychopathology. Another complication is the prevalence of cannabis use, which has increased from 3 percent to 7 percent among pregnant women between 2002 and 2017.
The researchers used statistical methods to rule out some of these confounding factors and suggest potential biologically based relationships between prenatal cannabis exposure and types of adolescent behavior.
While it’s not possible to prove 100 percent causal, “we can examine the plausibility of a causal relationship and suggest that it may be plausible by identifying potential biological correlates that relate cannabis exposure to these mental health effects,” Bogdan said of the study’s findings.
The researchers used data from the Adolescent Brain and Cognitive Development (ABCD) Study, an ongoing research project involving nearly 12,000 children across the U.S. As part of the study, the researchers collected data on maternal substance use before birth, as well as neuroimaging data when the children were 9-10 and 11-12 years old. About 370 children were exposed to marijuana before their mothers knew they were pregnant, and 195 children were exposed both before and after their mothers knew they were pregnant.
The researchers looked at a variety of neuroimaging measures important to brain development, including brain thickness and surface area, as well as measures of water diffusion in and out of cells, and the patterns they saw in the group of children exposed prenatally to cannabis are consistent with a potential reduction in neuroinflammation.
“What we’re seeing is an anti-inflammatory effect of cannabis that may be making a difference in how the brain is pruned during neurodevelopment,” Bogdan said.
Despite the much-touted anti-inflammatory effects of cannabis, it’s not necessarily good for reducing inflammation. Timing is key: Reducing inflammation too much at the wrong time can impact brain pruning and readiness.
Another theory is that cannabis exposure accelerates aging, but we don’t expect to find conclusive biological evidence that mental illness is caused by early cannabis exposure.
It may not be a matter of pruning, and it’s not the cannabis use itself that causes the post-combustion products of smoking cannabis that could accelerate aging and cause later cognitive effects, Bogdan said.
Or maybe it’s all sociological.
Finding one-to-one associations that prove prenatal cannabis exposure has adverse effects on teens will be difficult and may not be possible in retrospective studies. Baranger points out that the main limitation of this dataset is that it is retrospective; mothers reported cannabis use going back 10 years, and he hopes for new data from prospective longitudinal studies that provide more recent, accurate, and detailed information on cannabis use during pregnancy.
“This may provide further answers to these questions in the future.”
Meanwhile, the study’s findings reaffirm that if you’re considering using marijuana during pregnancy, “talk to your doctor about your choices and what other options are available to you,” Baranger said.
sauce:
Washington University in St. Louis
Journal References:
Balanger, DAA, other(2024). Prenatal cannabis exposure, the brain, and early adolescent psychopathology. Nature Mental HealthSource: http://www.dept.gov/depts…