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Marijuana and the Developing Brain

U.S. Surgeon General encourages young people and pregnant women not to use marijuana
By Josh Devine, PharmD, PhD, and Lesley J. Craig, MPH

IN AUGUST 2019, the Surgeon General issued an advisory focused on the importance of protecting youth and pregnant women from the health risks of marijuana use:

“I, Surgeon General VADM Jerome Adams, am emphasizing the importance of protecting our nation from the health risks of marijuana use in adolescence and during pregnancy. Recent increases in access to marijuana and in its potency, along with misperceptions of safety of marijuana endanger our most precious resource, our nation’s youth.”

Marijuana, or cannabis, is the most commonly used illicit drug in the U.S. Delta-9-tetrahydrocannabinol (THC), a component of marijuana, binds to cannabinoid receptors in the brain, resulting in euphoria, intoxication, and memory and motor impairments. These same cannabinoid receptors are critical for brain development. They are part of the endocannabinoid system, which impacts the formation of brain circuits important for decision-making, mood, and stress-response.

Marijuana has changed over time and newer strains have shown to have higher concentration of THC; in commonly cultivated marijuana plants THC concentration has increased three-fold between 1995 and 2014 from 4% to 12% respectively. Additionally, concentrated products, typically referred to as dabs or waxes, are much more widely available to recreational users today and may contain between 23.7% and 75.9% THC. Exposure to increasingly potent strains are more likely to produce other risks like anxiety, agitation, paranoia and psychosis.

Marijuana Use During Adolescence
Marijuana continues to be the most widely used illicit drug. In 2017, approximately 9.2 million 12- to 25-year-olds reported using marijuana in the past month and 29% more young adults aged 18 to 25 started using the substance.

The human brain continues to develop from before birth into the mid-20s and frequent use of marijuana during adolescence is linked to changes in brain areas involved in attention, memory, decisionmaking, and motivation. Marijuana use in youth is often also associated with other substance use including heavy alcohol use, and in 2017, 12- to 17-year-olds who reported frequent use of marijuana showed a 130% increase in likelihood of misusing opioids. Additionally, regular use in youth and young adults appears to be associated with major depressive episodes and suicide attempts.

Marijuana Use During Pregnancy
A national survey found that marijuana use in the past month among pregnant women doubled from 3.4% to 7% between 2002 and 2017.  Marijuana is used by pregnant women more than any other illicit drug.

Marijuana use during pregnancy can impact the developing fetus; THC can enter the fetal brain from the mother’s bloodstream and may disrupt the endocannabinoid system, which is important for a healthy pregnancy and fetal brain development. The Colorado Pregnancy Risk Assessment Monitoring System (PRAMS) found that regardless of maternal age, race, ethnicity, education, and tobacco use, maternal marijuana use was associated with a 50% increased risk of low birth weight. Both the American College of Obstetricians and Gynecologists and the American Academy of Pediatrics recommend that physicians advise patients to discontinue or not use marijuana during pregnancy.

It is important to note that maternal marijuana use may still have negative effects on a baby after birth. THC has been found in breast milk up to six days after the last recorded use. It may impact newborn brain development and result in hyperactivity, poor cognitive function, and other long-term consequences. As with tobacco, marijuana should not be smoked around a baby; it contains many of the same harmful components as tobacco smoke.

The purpose of the recent advisory from the Surgeon General is to promote awareness of the known and potential harms to developing brains that are posed by the increasing availability of highly potent marijuana in multiple, concentrated forms. The advisory includes recommended action items for clinicians and other healthcare professionals, along with parents and parents-to-be, young people, and different communities.

Recommendations for clinicians include asking patients about marijuana use, integrating marijuana education in prenatal and postpartum visits, and informing mothers-to-be, new mothers, youth, and all patients vulnerable to psychotic disorders of the risks of marijuana use.

Safe and effective treatments exist for nausea, pain, and depression during pregnancy and can be prescribed. While more research is needed to understand how THC impacts the developing brain, current findings warrant attention and action by healthcare professionals.

Everyone can contribute to the protection of the next generation from the risks of marijuana. Learn more about the Surgeon General’s Advisory and find resources to help you take action at www.

Josh Devine, PharmD, PhD, is a captain in the U.S. Public Health Service and Regional Health Administrator, and Lesley Craig, MPH, is a public health advisor at the U.S. Department of Health and Human Services (HHS), Office of the Assistant Secretary for Health (OASH) – Region 5 (IL, IN, MI, MN, OH, WI). Contact us at Lesley.Craig@

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