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April 30, 2019
by Patricia Tomasi

New Study Finds Prenatal Marijuana Exposure Is Associated With A Small Increase In Psychosis In Children

April 30, 2019 08:00 by Patricia Tomasi  [About the Author]

A new study published in JAMA Psychiatry examined whether maternal use of cannabis during pregnancy is associated with psychosis liability in offspring. 

We expected that cannabis use would be associated with increased psychosis proneness in offspring,” study author Ryan Bogdan told us. “However, we also expected that some of this relationship might be accounted for by other potentially related factors (e.g., other substance use during pregnancy, maternal education, family history of psychopathology, maternal prenatal vitamin use, child substance use, etc.).”

Bogdan is an Associate Professor at BRAIN Lab at Washington University in St. Louis, Missouri. He told us that he chose to do the study because alongside increasingly permissive marijuana use attitudes and laws, the prevalence of marijuana use among pregnant mothers has increased substantially (by 75% between 2002 and 2016).

“Further, there is some evidence that dispensaries recommend using cannabis to combat pregnancy-related nausea and that pregnant women report using marijuana during pregnancy for this purpose,” Bogdan told us. “However, very little is known how this may affect the developing fetus and child.” 

Tetrahydrocannabinol (THC), which is the principal psychoactive component of marijuana, mimics our body’s endocannabinoids and binds to endocannabinoid receptors to exert its effects, Bogdan explained. Given that the endocannabinoid system critically contributes to neurodevelopment and evidence that THC crosses the placenta to access the developing fetus, he says we need to better understand the potential impact of prenatal cannabis exposure. 

Researchers used data from a national U.S.-based data collection project, the Adolescent Brain and Cognitive Development (ABCD) study which is an ongoing longitudinal study of child health and brain development. They used the initial ABCD baseline data release which included survey responses from 3,774 mothers about marijuana usage during 3,926 pregnancies. Risk of psychosis in the 4,361 children born from these pregnancies between 2005 and 2008 was measured using a questionnaire administered to the children between ages 8.9 and 11 years. 

“We found that prenatal marijuana exposure after maternal knowledge of pregnancy is associated with a small increase in psychosis proneness during middle childhood (~ age 10),” Bogdan told us. “Interestingly, we found that maternal use of cannabis during pregnancy before and after knowledge of pregnancy was correlated with increased psychosis proneness in children. However, after we accounted for potentially confounding factors (e.g., other substance use during pregnancy, maternal education, family history of psychopathology, maternal prenatal vitamin use, child substance use, etc.), only use after maternal knowledge of pregnancy was associated with increased psychosis proneness in children.”

In addition to differences in mothers who continue to use following knowledge of pregnancy that were not accounted for in their study (e.g., maternal stress exposure), another possible explanation for this pattern of association is endocannabinoid system development, Bogdan explained. Data from rodents suggest that the endocannabinoid type 1 receptor, through which the psychoactive effects of THC largely arise, is not expressed until the equivalent of 5-6 weeks of human gestation.

“Given that mothers in our study on average learned of their pregnancy at 7.7 weeks,” Bogdan told us, “it is plausible that any impact of THC on psychosis risk would not arise until sufficient endocannabinoid type 1 receptors are expressed.”

Although Bogdan says he and his colleagues were fortunate to work with the large national adolescent brain and cognitive development (ABCD) study dataset which provided them with data for one of the largest investigations of psychosis proneness and prenatal marijuana exposure, he says it is also important to interpret these results in the context of study limitations including the small sample of prenatal cannabis-exposed offspring, reliance on retrospective self-report for prenatal use, and imprecise data on the timing, amount, frequency, and potency of prenatal cannabis exposure and the lack of data on other potential confounding variables (e.g., stress during pregnancy, paternal factors).

“This research is strictly correlational and cannot draw causal conclusions,” Bogdan told us. “However, that the association remained after accounting for a host of potentially confounding factors (e.g., maternal education, family history of psychopathology, age at pregnancy, birth weight, prenatal vitamin use, alcohol and nicotine use during pregnancy, etc.), increases the plausibility that prenatal cannabis exposure may contribute to a small risk of increases psychosis proneness among children. Until more research accumulates, these data suggest that marijuana use during pregnancy should be discouraged.”    

Given increasing cannabis accessibility and potency as well as perceptions of safety, it is critical for additional research to understand the potential adverse consequences and benefits of cannabis throughout development and how these associations may arise, Bogdan explained. In the meantime, evidence that prenatal marijuana use is associated with a small increase in offspring psychosis proneness suggest that marijuana use during pregnancy should be discouraged until more is known.


About the Author

Patricia Tomasi

Patricia Tomasi is a mom, maternal mental health advocate, journalist, and speaker. She writes regularly for the Huffington Post Canada, focusing primarily on maternal mental health after suffering from severe postpartum anxiety twice. You can find her Huffington Post biography here. Patricia is also a Patient Expert Advisor for the North American-based, Maternal Mental Health Research Collective and is the founder of the online peer support group - Facebook Postpartum Depression & Anxiety Support Group - with over 1500 members worldwide. Blog:

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