Marijuana Use During Pregnancy Linked to Children’s Mental Health Disorders: Study

Researchers expressed concern over growing marijuana use during pregnancy nationwide, which can increase the risk of ADHD, aggressive behavior and other problems among children

Children whose mothers used marijuana during pregnancy, even early in the first trimester, are more likely to suffer mental health problems as teens, according to the findings of a new study.

In a report published this week in the medical journal JAMA Pediatrics, researchers from Washington University in St. Louis tracked 12,000 children as they grew into young adults, and found that exposure to marijuana during pregnancy increased the risk of aggressive behavior, conduct disorders, and attention deficit hyperactivity disorder (ADHD).

Researchers used data from the Adolescent Brain Cognitive Development Study, the largest long-term study of brain development and health in children and teens in the US, measuring participants’ brain structure and activity using magnetic resonance imaging (MRI). They also collected psychological, environmental, and cognitive information as well as biological samples.

The data indicated prenatal exposure to cannabis was linked to an increased risk of ADHD, as well as social and behavioral problems that persisted into adolescence. Researchers determined that marijuana use as early as five to six weeks into pregnancy, during the middle of the first trimester, was linked to negative side effects.

Infants exposed to marijuana early in pregnancy had a greater risk of mental health disorders and substance use in late adolescence, according to the findings. The findings add to a growing body of evidence indicating marijuana use during pregnancy carries risks for the fetus that can persist into adolescence.

Cannabis use among pregnant women has increased in recent years, rising from 3% in 2002 to 7% in 2017. By 2018, roughly 4.7% of women used cannabis and in 2019, about 5.4% said they used marijuana during pregnancy, according to data from the National Survey on Drug Use and Health.

The findings of the new study do not prove cannabis caused the mental health problems, but indicates there is cause for concern, researchers concluded.

THC Crosses Placenta and Brain Barrier

The tetrahydrocannabinol (THC) in cannabis can cross the placenta and affect brain development. During early pregnancy, cannabinoid receptors are widely expressed in the brain, making them more receptive to THC and to any changes that can occur because of exposure.

An earlier analysis of the research in the ongoing ABCD study highlighted a link between prenatal exposure and behavioral problems in children at ages 9 and 10. Children exposed to cannabis also had lower birth weight, lower brain volume and lower white matter volume.

Other research published last year indicated marijuana use during pregnancy was linked to an increased risk of mental health and behavioral issues among the children. The children showed elevated levels of stress, aggression and hyperactivity at a young age.

As states move to legalize marijuana, researchers warn more pregnant women may be using it during pregnancy. Some dispensaries suggest it can help women combat nausea during pregnancy and tout its safety during pregnancy. However, this and other recent research indicates otherwise.

“Dramatic increases in cannabis use during pregnancy are alarming because of evidence that prenatal exposure may be associated with a hose of adverse outcomes,” the researchers warned.