Prenatal THC Exposure May Disrupt Brain Signaling

Cannabis use during pregnancy remains one of the most debated topics in public health. As legalization expands and perceptions of cannabis safety continue to shift, more researchers are working to understand how exposure to cannabinoids during fetal development may influence the growing brain.

While scientists have long known that the endocannabinoid system plays an important role in brain development, many questions remain about what happens when external cannabinoids like THC enter the picture during pregnancy. New research is now providing a closer look at the biological mechanisms involved, revealing changes that may extend far beyond birth.

A 2026 preclinical study¹ published in the Journal of Biological Chemistry investigated how prenatal THC exposure affects communication between brain cells. The findings suggest that exposure during development may alter critical signaling pathways in the hippocampus, potentially reshaping how neural circuits form and function later in life. Let’s dive into the research and what it means moving forward.

Why Brain Signaling Balance Matters

The brain relies on a delicate balance between two major forms of communication: excitation and inhibition. Excitatory signals encourage neurons to fire and transmit information, while inhibitory signals help regulate activity and prevent excessive stimulation. Together, these systems create the foundation for healthy brain function. When excitation and inhibition remain in balance, neural networks can efficiently process information, form memories, and adapt to new experiences. If that balance becomes disrupted, however, communication between neurons can become less effective.

Scientists often refer to this relationship as the “excitation-inhibition balance” or E/I balance. Increasingly, researchers believe that disturbances in this system during development may influence cognitive function later in life.

How Researchers Studied Prenatal THC Exposure

To better understand the effects of prenatal cannabis exposure, researchers used a rodent model in which offspring were exposed to THC during fetal development. The team then examined the animals during adolescence, focusing on the hippocampus. This region of the brain plays a major role in memory formation, learning, and spatial navigation.

The researchers evaluated memory performance, measured electrical activity between neurons, and analyzed proteins involved in communication at synapses, the specialized junctions where brain cells exchange signals. Their goal was not simply to determine whether THC exposure affected behavior, but to uncover the biological mechanisms that might explain any observed changes.

Prenatal THC Exposure and Memory Deficits

One of the most notable findings involved memory performance. Animals exposed to THC before birth demonstrated deficits in hippocampal-dependent memory tasks during adolescence compared to control groups. The researchers also found changes in synaptic plasticity, a process often described as the brain’s ability to strengthen or weaken connections between neurons in response to experience.

Two important forms of synaptic plasticity were affected:

• Long-term potentiation (LTP), which helps strengthen neural connections associated with learning and memory, was impaired.
• Long-term depression (LTD), which weakens certain connections as part of normal brain adaptation, was increased.

Together, these findings suggest that prenatal THC exposure may alter the brain’s ability to modify and refine neural circuits as it matures.

THC Altered Key Glutamate Signaling Pathways

A major focus of the study involved glutamate, the brain’s primary excitatory neurotransmitter. Glutamate is critical for learning, memory formation, and communication between neurons. It works by activating specialized receptors that help transmit signals across synapses.

The researchers discovered reduced activity in signaling mediated by AMPA receptors, which are essential components of excitatory neurotransmission. They also observed lower levels of several postsynaptic proteins associated with glutamate signaling, including:

• GluA1
• GluN2A
• GluN2B
• PSD95

Interestingly, markers associated with presynaptic glutamate release remained largely unchanged. This pattern suggests that prenatal THC exposure may primarily affect how receiving neurons respond to excitatory signals rather than how those signals are initially released.

In practical terms, the findings indicate that important pathways involved in learning and memory may become less efficient following prenatal THC exposure.

Changes in GABA Signaling May Shift Brain Activity

The study found evidence that inhibitory signaling increased relative to excitatory signaling. This effect was linked to changes involving GABA, the brain’s primary inhibitory neurotransmitter. GABA helps calm neural activity and prevents excessive firing within brain circuits. While inhibitory signaling is essential for healthy brain function, too much inhibition relative to excitation can alter how information flows through neural networks.

Electrophysiological testing revealed a shift toward greater inhibitory influence within the hippocampus, contributing to the overall excitation-inhibition imbalance observed by the researchers. The findings suggest that prenatal THC exposure may not simply reduce excitatory activity but may also strengthen inhibitory influences, creating a dual effect on circuit function.

Structural Changes Were Found in the Hippocampus

Beyond functional changes in signaling, researchers identified evidence of physical remodeling within hippocampal circuitry. Particularly noteworthy were alterations involving the CB1 receptor, one of the primary receptors through which THC exerts its effects.

The team observed region-specific changes in the distribution of CB1 receptors and their relationship with vesicular GABA transporter (VGAT), a protein involved in inhibitory neurotransmission. These findings suggest that prenatal THC exposure may influence how inhibitory networks are organized during development. Rather than causing a single isolated change, THC exposure appeared to trigger a coordinated restructuring of multiple systems involved in neural communication. This combination of functional and anatomical changes may help explain why memory deficits persisted into adolescence in the study animals.

What These Findings Mean for Cannabis Use During Pregnancy

The results add to a growing body of evidence suggesting that prenatal THC exposure can influence brain development in ways that extend beyond birth.

Importantly, this was a preclinical animal study, meaning the findings cannot be directly translated to human pregnancy outcomes. Human brain development is more complex, and many additional factors, including genetics, environment, dosage, frequency of use, and timing of exposure, can influence outcomes.

However, the study offers valuable insight into potential biological mechanisms that may underlie developmental effects observed in previous research. By identifying changes in glutamate signaling, GABA signaling, synaptic plasticity, and hippocampal circuitry, the researchers provide a clearer picture of how THC may affect the developing brain at the cellular level.

The Future of Prenatal Cannabis Research

As cannabis use becomes increasingly common, researchers continue working to understand its effects across different stages of life, including pregnancy. This study highlights the importance of looking beyond broad behavioral outcomes and examining the underlying biology that shapes brain development. The findings suggest that prenatal THC exposure may alter the balance of neural signaling systems that help build healthy brain circuits, potentially affecting memory and learning later in life.

While more research, particularly human studies, is needed, these results contribute an important piece to the larger puzzle. As scientists continue exploring how cannabinoids interact with the developing brain, studies like this may help guide future recommendations, improve public health education, and identify potential strategies for addressing developmental challenges linked to prenatal exposure.

References:

^{1. Priyanka D. Pinky, Warren D. Smith, Miles T. Wiley, Jenna Bloemer, Vasiliki Syropoulou, Iva Durdanovic, Sharay E. Setti, Jeremiah C. Pfitzer, Savannah R. Perman, Kawsar U. Chowdhury, Kelli L. McDonald, Michael W. Gramlich, Subhrajit Bhattacharya, Vishnu Suppiramaniam, Miranda N. Reed, Prenatal cannabinoid exposure alters excitation-inhibition balance through glutamate and GABA receptor-mediated signaling, Journal of Biological Chemistry, 2026, 113196, ISSN 0021-9258, https://doi.org/10.1016/j.jbc.2026.113196}