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Cannabis Use in Pregnancy Tied to Small Increased Risk of Psychosis in Offspring

April 05, 2019

By Marilynn Larkin

NEW YORK—Cannabis use during pregnancy is associated with a small increase in psychosis proneness in children, researchers say.

"This research is strictly correlational and cannot draw causal conclusions," Dr. Ryan Bogdan of Washington University in St. Louis, Missouri told Reuters Health by email. "However, this association remained after accounting for a host of potentially confounding factors - e.g., maternal education, age at pregnancy, birth weight, prenatal vitamin use, alcohol and nicotine use during pregnancy, etc. - which increases the plausibility (of the findings)."

"Until more research accumulates," he said, "these data suggest that marijuana use during pregnancy should be discouraged."

Dr. Bogdan and colleagues analyzed data from the ongoing Adolescent Brain Cognitive Development Study to assess whether maternal report of cannabis use during pregnancy was associated with psychosis proneness as measured by the self-report Prodromal Questionnaire-Brief Child Version score.

As reported online March 27 in JAMA Psychiatry, the study involved 4,361 children (mean age at baseline, 10 years; 47% girls), including 201 (4.61%) who were prenatally exposed to marijuana. Of that subset, 138 (69%) were exposed only before maternal knowledge of pregnancy; 61 (30%) were exposed before and after maternal knowledge; and two (less than 1%) were exposed only after maternal knowledge.

As Dr. Bogdan noted, marijuana use after knowledge of pregnancy was associated with increased offspring psychosis proneness in models with and without potential confounders such as maternal alcohol and tobacco use during pregnancy, maternal education, household income, family history of psychosis, unplanned pregnancy, and child tobacco/alcohol exposure.

Further analyses revealed no link between prenatal exposure after pregnancy knowledge and offspring internalizing, externalizing, or attention symptoms. reported on the Child Behavior Checklist.

Study limitations include the small sample of prenatal cannabis-exposed offspring, potential underreporting by mothers of cannabis use during pregnancy; and imprecise data on the timing, amount frequency and amount of cannabis exposure.

"There are many different factors associated with psychosis risk that likely exert independent, additive, and interactive small effects," Dr. Bogdan said. "For example, some children may be at greater risk for psychosis proneness related to prenatal cannabis exposure due to genetic or environmental factors. It will be important to identify such individual difference factors that may increase or decrease risk in future work."

"Given increasing accessibility and potency of marijuana and the shift of laws and attitudes towards increased permissiveness," he noted, "it is important to understand potential adverse consequences and benefits of cannabis throughout development and how these associations may arise."

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

"Our evidence that prenatal marijuana exposure is associated with increased risk for psychosis liability is particularly concerning given evidence that some dispensaries recommend using cannabis to combat pregnancy-related nausea," Dr. Bogdan concluded.

Dr. Gary Wenk, Professor of Psychology and Neuroscience at The Ohio State University College of Medicine in Columbus and Director of Ohio State's Neuroscience Programs, said in an email to Reuters Health that the study findings are feasible "as long as the exposure occurred during a vulnerable time in the development of a brain region or critical transmitter system and that the dose of marijuana (no one can be certain which of the 4,550 different components of the plant might be responsible) was sufficient to produce some detectable effect."

Like Dr. Bogdan, Dr. Wenk noted, "The study did not independently determine whether any children carried a genetic predisposition. In addition, the study relies upon an accurate memory by the mothers about their long past marijuana use and its timing with pregnancy."

Clinicians should not tell pregnant women about the findings, said Dr. Wenk, who is also a member of the Ohio Medical Marijuana Advisory Committee, "until they are confirmed and expanded to include insights that could offer a potential mechanism regarding how this long-lasting impairment occurs."


JAMA Psychiatry 2019.

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