When cannabis is inhaled, consumed orally or taken in through other routes, it can easily cross through the placenta and deposit in the fetal brain, disrupting brain development.

A recent study from my lab, led by medical student Mohammed Faraj, found that cannabis use during pregnancy can shape the developing brain in ways that are detectable even a decade later.

We used data from the National Institutes of Health Adolescent Brain Cognitive Development Study, which is the largest long-term study of brain development and child and adolescent health in the U.S. It has followed more than 10,000 children and their families from age 9-10 over a 10-year period.

Through that analysis, we linked prenatal cannabis exposure to alterations in functional brain networks in 9- and 10-year-old children. In particular, prenatal cannabis exposure appeared to disrupt the communication between brain networks involved in attentional control, which may explain why children who were exposed to cannabis in utero may develop difficulties with attention or other behavioral issues or mental disorders as they develop.

While alcohol abuse has steadily declined among adolescents since 2000 in the U.S., cannabis use shows the opposite pattern: It increased by 245% during that same period.

Data reported in 2022 from the Monitoring the Future survey of over 50,000 students in the U.S. found that nearly one-third of 12th grade students reported using cannabis in the past year, including cannabis vaping. Yet only about 1 in 4 12th grade students perceive great harm in using cannabis regularly. This suggests that many teens use cannabis, but very few consider it to have potential negative effects.

Research shows that the adolescent brain is primed to engage in high-risk behaviors such as experimenting with cannabis and other substances. Unfortunately, owing to ongoing brain development, the adolescent brain is also particularly susceptible to the effects of cannabis and other substances. Indeed, many neuroscientists now agree that the brain continues to develop well into the second and even third decade of life.

In line with this vulnerability, research shows that, relative to those who did not use cannabis during adolescence, those who started using it during adolescence are at increased risk of developing depression, suicidal ideation, psychosis and reductions in IQ during adolescence and adulthood. Neuroimaging studies also show residual effects of adolescent cannabis use on brain functioning, even later during adulthood.

Despite common misconceptions that cannabis is “all natural” and safe to use during pregnancy or adolescence, the data suggests there are real risks. In fact, in 2019, the U.S. surgeon general issued an advisory against the use of cannabis during pregnancy and adolescence, stating that “no amount … is known to be safe.”

Cannabis may be harmful to the developing brain because it disrupts the developing endocannabinoid system, which plays a critical role in shaping brain development from conception and into adulthood. This includes neural circuits involved in learning, memory, decision-making and emotion regulation.

While much of this research has focused on cannabis use, there is also other research that comes to similar conclusions for THC and CBD in other forms. In fact, although CBD is widely available as an unregulated supplement, we researchers know almost nothing about its effects on the developing brain. Of note, these harms apply not only to smoking, but also to ingesting, vaping or other ways of consuming cannabis or its extracts.

In my view, it’s important that consumers know these risks and recognize that not everything claimed in a label is backed by science. So before you pick up that edible or vape pen for stress, anxiety, or sleep or pain control, it’s important to talk to a health care provider about potential risks – especially if you are or could be pregnant or are a teen or young adult.

This article is republished from The Conversation, an independent nonprofit news site dedicated to sharing ideas from academic experts. Like this article? Subscribe to our weekly newsletter.

Read more:
Marijuana and pregnancy: There’s no evidence that exposure is safe

How does smoking marijuana affect academic performance? Two researchers explain how it can alter more than just moods

Hilary A. Marusak receives funding from the National Institutes of Health and the State of Michigan.