Study: Cannabis use during pregnancy may harm child's long-term mental health

Sept. 12 (UPI) -- Offering a cautionary tale to pregnant individuals who think smoking a joint is no big deal, new research links prenatal cannabis exposure to social, emotional and behavioral problems in offspring that may persist into early adolescence: ages 11 to 12.

Researchers analyzed roughly a dozen measures, ranging from rule-breaking to aggression, a "sluggish cognitive tempo" and "psychotic-like experiences."

In a research letter published Monday in JAMA Pediatrics, the investigators said the affected children also may face a greater risk of "psychiatric disorders and problematic substance use" as they enter the peak period of vulnerability in later adolescence.

For the study, researchers from Washington University in St. Louis analyzed data from the ongoing Adolescent Brain Cognitive Development Study of 12,000 youth, the largest long-term study of brain development and children's health in the United States.

Investigators also cited a national survey indicating that U.S. cannabis use among pregnant women nearly doubled to 5.4% in 2019 from 3% in 2002.

"Dramatic increases in cannabis use during pregnancy are alarming because of evidence that prenatal exposure may be associated with a host of adverse outcomes," wrote the letter's lead author, David Baranger, a neuroscientist and postdoctoral researcher in Washington University's Department of Psychological and Brain Sciences.

The study included 391 women who used cannabis only before they knew they were pregnant, 208 who used the drug before and after they knew, and just over 10,000 with no exposure to it. Modeling was used to estimate associations with child psychopathology.

The researchers acknowledged the study's limitations, including the small number of offspring exposed to cannabis in utero, the potential under-reporting of cannabis use during pregnancy, and imprecise data on drug use timing, frequency and potency.

Yet, they pointed to a 2020 research using baseline data from the ABCD Study that found an association between prenatal marijuana exposure and behavioral problems in the children at 9 to 10 years of age.

Also cited were previous preclinical studies indicating delta-9-tetrahydrocannabinol, or THC, the main psychoactive substance in cannabis, can cross the placenta and potentially affect brain development in the fetus.

The ABCD Study participants' brain structure and activity are regularly measured using magnetic resonance imaging. Investigators also "collect psychological, environmental and cognitive information, as well as biological samples," a news release said.

The ABCD Study aims to determine the factors that influence brain, cognitive and social-emotional development in an effort to help improve children's lives, the release said.