Cannabis use during pregnancy rewires the fetal brain

THC, the main psychoactive ingredient in cannabis, is being used by more pregnant women as the legalization of recreational cannabis gains ground. Women who are expecting often use cannabis for morning sickness, lower back pain, or anxiety relief.

Recent figures indicate that up to 1 in 5 pregnant women in the U.S. now use cannabis. However, growing research suggests that THC exposure could pose significant risks to the developing fetus.

A recent study highlights how prenatal exposure to THC may increase the risk of opioid addiction later in life.

THC rewires the fetal brain

The preclinical animal study, led by researchers at the University of Maryland School of Medicine and published in the journal Science Advances, revealed that prenatal exposure to THC rewires the fetal brain.

According to the study, THC made certain dopamine neurons hyperactive, resulting in a marked increase in dopamine release and an amplified response to reward-related cues, such as a signal indicating the availability of food or an opioid drug.

“Doctors are contending with an explosion of cannabis use, and the THC content has quadrupled from what it was a generation ago,” said Dr. Joseph Cheer, a professor of Neurobiology and Psychiatry at the University of Maryland School of Medicine.

“It demonstrates the enduring consequences that prenatal cannabis exposure exerts on the brain’s reward system, which ultimately results in a neurobiological vulnerability to opioid drugs.”

Prenatal exposure to THC

The study revealed that prenatal exposure to THC led to significant changes in the brain’s reward system, particularly in male animals.

These animals displayed an exaggerated surge in the “reward-seeking” brain chemical dopamine when exposed to opioid drugs during adolescence, compared to those not exposed to THC.

Even moderate doses of THC – equivalent to one to two joints per day in humans – altered how the fetal brain processed rewards, fostering behavior suggestive of increased opioid-seeking.

This behavior was confirmed by follow-up experiments where tiny sensors implanted in their brains detected heightened dopamine release and over-activation of neurons linked to reward-seeking behavior.

“These observations support the hypothesis of a hypersensitized ‘wanting’ system that develops in the brain after exposure to THC during prenatal development,“ said Dr. Cheer.

“Interestingly, we found that this opioid-seeking phenotype occurs significantly more in males compared to females, and we are currently performing research with our colleagues at UMSOM to determine why this is the case.”

Advancing research and guidance

Dr. Cheer and his colleague, Dr. Mary Kay Lobo, co-direct the Center for Substance Use in Pregnancy at the University of Maryland School of Medicine’s Kahlert Institute for Addiction Medicine.

Their ongoing research aims to further understand the long-term impact of drug exposure during pregnancy.

“We need to more fully understand the enduring effects of THC exposure in the womb and whether we can reverse some of the deleterious effects through CRISPR-based gene therapies or repurposed drugs,” said study co-author Dr. Dean Mark T. Gladwin.

“We also need to provide better advice to pregnant patients, many of whom are using cannabis to help control anxiety because they think this drug is safer for their baby than traditional anti-anxiety medications.”

Cannabis use during pregnancy

The findings suggest that there is a need for more exhaustive public health programs to educate pregnant women on the long-term effects that coincide with marijuana exposure during pregnancy.

Previous studies on cannabis use during pregnancy have also raised significant concerns about its potential impacts on fetal development and maternal health.

For example, studies have linked prenatal cannabis exposure to deficits in attention, memory, and executive functioning in children.

Furthermore, cannabis use during pregnancy is associated with an increased risk of low birth weight, which can lead to complications such as developmental delays and long-term health issues.

Guidelines on pregnancy and provision of adequate resources for pregnant women could be created and harmonized in collaboration between healthcare providers, researchers, and policymakers.

Investments in supplemental research, which would include human studies, may also clarify how exposures to THC impact the fetal brain in its developing state.

The study is published in the journal Science Advances.

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