Prenatal cannabis exposure may delay the developmental transition of GABA from an excitatory to inhibitory signal—a critical switch that guides how neurons wire together in the developing brain.
Developmental neuroscientists, neonatologists, obstetricians counseling about prenatal cannabis, and researchers studying GABA in brain development.
What the researchers found
This review presents a fascinating and underappreciated mechanism by which prenatal cannabis could affect brain development: the GABA switch.
Here's the background: during early brain development, GABA—which becomes the brain's primary inhibitory neurotransmitter in adults—actually functions as an excitatory signal. This seems counterintuitive, but it's essential: excitatory GABA drives critical developmental processes including neuron proliferation, migration, and circuit formation. At a specific developmental timepoint, GABA switches from excitatory to inhibitory. This switch is precisely timed and essential for normal brain maturation.
The review's central finding: exposure to exogenous cannabinoids (like THC) can delay this GABA switch. Because THC crosses the placenta and interacts with the endocannabinoid system—which modulates GABA signaling—it disrupts the timing of a process that needs to happen at exactly the right moment.
The consequences of a delayed GABA switch could be far-reaching. If GABA remains excitatory too long, neurons may proliferate or migrate incorrectly, circuits may wire abnormally, and the foundation for later cognitive and emotional function may be compromised. The review connects this mechanism to the clinical observations of hyperactivity, attention issues, anxiety, depression, and reduced cognitive abilities documented in children exposed to cannabis prenatally.
Why it matters
The delayed GABA switch mechanism could explain a wide range of neurodevelopmental effects attributed to prenatal cannabis exposure. Rather than cannabis simply being 'toxic' to the developing brain, it may be disrupting the precise timing of a normal developmental process—which is potentially even more consequential because it affects the foundation on which all subsequent brain development is built.
The numbers in context
Cannabis is the most commonly used illicit drug during pregnancy. THC crosses the placenta and affects the fetal endocannabinoid system. Prenatal exposure linked to: hyperactivity, attention issues, anxiety, depression, reduced cognitive abilities. GABA transition from excitatory to inhibitory is a critical developmental switch.
How the study worked
Narrative review synthesizing evidence on the effects of exogenous cannabinoids on the endocannabinoid and GABAergic systems during neurodevelopment. Focuses on the developmental GABA excitatory-to-inhibitory switch and the consequences of its disruption.
Who was studied
Review of effects related to cannabis use during pregnancy on fetal neurodevelopment.
What this study cannot tell us
Much of the GABA switch evidence comes from animal models and in vitro studies. The exact timing and mechanism of the GABA transition vary across brain regions and species. Whether THC exposure at typical human doses is sufficient to delay the switch is uncertain. The review doesn't quantify how much delay in the GABA switch is clinically meaningful. Narrative review format is subject to selection bias.
How to read the evidence
Narrative review of preclinical and mechanistic evidence—presents a compelling hypothesis but requires more direct evidence of the GABA switch delay in human pregnancies.
When this study was published
Published in 2025, incorporating recent findings on the GABA developmental transition.
The bigger picture
This provides a unifying mechanism for the diverse neurodevelopmental effects catalogued in RTHC-00209 (prenatal cannabis review) and RTHC-00216 (reproductive effects review). RTHC-00191's finding that timing of prenatal THC exposure matters for amygdala development may be related to the GABA switch timeline in specific brain regions. RTHC-00210's discovery that CB1 activation reduces GABA in the adult prefrontal cortex shows the endocannabinoid-GABA interaction persists throughout life—but during development, disrupting it is particularly consequential.
Replication
Not stated in abstract.
Funding
Not reported in abstract.
Conflicts of interest
Not reported in abstract.
Questions still open
- Is the delayed GABA switch reversible after birth, or does it permanently alter brain wiring? Does the dose and timing of prenatal THC exposure determine the severity of the delay? Could the GABA switch mechanism become a target for interventions in exposed neonates?
Read the original research
Neurodevelopmental effects of exogenous cannabinoids on endocannabinoid and GABAergic neurotransmission.
Neurotoxicology and teratology, 112, 107568
Neurotoxicology and Teratology is a reputable journal focusing on the effects of toxic substances on development.
Citation
Wiley, Miles T; Courville, Adrian H; Northcutt, Hayden; Durdanovic, Iva; Chowdhury, Kawsar U; Suppiramaniam, Vishnu; Reed, Miranda N. (2025). Neurodevelopmental effects of exogenous cannabinoids on endocannabinoid and GABAergic neurotransmission.. Neurotoxicology and teratology, 112, 107568. https://doi.org/10.1016/j.ntt.2025.107568
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