Prenatal Cannabis Exposure (PCE) Linked to Opioid Addiction Vulnerability in Fetuses

In a recent preclinical animal study, researchers from the University of Maryland School of Medicine (UMSOM) have shared results from a study¹ that found cannabis use during pregnancy, aka ‘Prenatal Cannabis Exposure’ or ‘PCE,’ can increase the fetus’ vulnerability to opioid addiction once grown.  This is particularly concerning, as recent surveys have found that not only is cannabis significantly more potent than it used to be, but an increasing amount of pregnant women are consuming the drug.

Concerning Findings on Fetal Vulnerability

While this study can be seen as a stepping stone toward full human trials, it remains thorough and quite revealing.  The following are a few of the more noteworthy findings made by researchers when exposing animals to the equivalent of a mother smoking two joints in a day.

• Tetrahydrocannabinol (THC), the primary psychoactive ingredient in cannabis, crosses the Placenta
• Neural changes occurred, affecting reward pathways

These two findings made it clear that by crossing the placenta during pregnancy, THC has an obvious effect on the development of the fetal brain.  This was found to be particularly notable in the brain’s reward centers and resulting dopamine production.  Males, in particular, were more susceptible to this, showing a greater risk of addiction-like behaviours and relapse when exposed to opioids.  Although males were more heavily affected, all of the rats showed the following.

PCE Alters Reward Processing: Rats exposed to THC in utero displayed heightened motivation for food and opioid rewards, suggesting an increased effort to obtain these rewards.
Impulsivity: PCE rats exhibited higher impulsivity and struggled to control automatic reward-seeking behaviours, particularly males.
Addiction Vulnerability: PCE rats showed greater willingness to work for drug rewards and were more likely to relapse when exposed to drug-related cues.

When looked at as a whole, it was found that the findings aligned with existing human studies linking PCE to increased risks of hyperactivity, impulsivity, and addiction.

Key Commentary

Speaking on the findings of the study, corresponding author Joseph Cheer, PhD, a Professor of Neurobiology and Psychiatry at the UMSOM has stated,

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

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.

Expanding on the subject, UMSOM Dean Mark T. Gladwin, MD, points to key emerging technologies that could potentially play an important role in our approach to PCE.

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.

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.

Nothing is Free of Risk

For adults looking to alleviate symptoms like nausea, anxiety, chronic pain, etc., cannabis is often recommended as an effective alternative to OTC medications.  In many cases, this can be a wise decision. However, there are instances when usage should be reconsidered.  One example of this is in pregnant women.

While it may sound obvious at first that pregnant women should typically avoid cannabis, a lack of knowledge on its long-term effects on fetuses, combined with the plant commonly being portrayed as risk-free, has shown that, as mentioned, in recent years, there has been an uptick in usage within this demographic.  It also doesn’t help that cannabis is particularly adept at easing many pregnancy-related symptoms.

Only now, as legalization spreads and research into the plant’s benefits and risks can be more freely explored, are we developing a more accurate profile on cannabis.  Simply put, while the plant may afford many benefits to adults, pregnant women need to recognize that they are consuming for two, and what may be right for them will not necessarily be for the fetus.

If in doubt, consult with a medical professional.

Study Reference:

^{1. Luján, M. Á., Young-Morrison, R., Aroni, S., Katona, I., Melis, M., & Cheer, J. F. (2024). Dynamic overrepresentation of accumbal cues in food- and opioid-seeking rats after prenatal THC exposure. Science Advances, 10(eadq5652). https://doi.org/10.1126/sciadv.adq5652}