THC at concentrations found in drivers' blood caused neurotoxicity through oxidative stress in lab cells | Research

The takeaway

When human neuronal cells were exposed to THC concentrations matching levels found in the blood of drivers in traffic accidents, higher concentrations caused significant cell death, oxidative stress, mitochondrial damage, and early signs of programmed cell death.

Cannabis users concerned about brain health, driving safety researchers, and policymakers setting THC impairment limits.

THC at real-world driver blood levels reduced neuronal cell viability to 65-77%

What the researchers found

THC at 73.75 and 150 ng/mL significantly reduced cell viability (to 76.5% and 64.6% at 48 hours) and caused morphological changes. THC increased reactive oxygen species (peaking at 116.5% at 150 ng/mL), disrupted glutathione balance (GSH/GSSG ratio decreased 69.2%), increased lipid peroxidation (34.5%), and reduced antioxidant enzyme activities. Nuclear condensation and mitochondrial membrane depolarization indicated early apoptosis.

Why it matters

This study bridges the gap between traffic safety data and neuroscience by testing THC concentrations actually found in impaired drivers. The finding that these real-world concentrations cause measurable neurotoxicity provides biological context for why THC impairs driving and other cognitive functions.

The numbers in context

THC concentrations tested: 0.66, 20, 73.75, 150 ng/mL. Cell viability at 48h: 76.5% (73.75 ng/mL), 64.6% (150 ng/mL). ROS peak: 116.5% at 150 ng/mL. GSH/GSSG ratio decreased 69.2%. Lipid peroxidation increased 34.5%. Antioxidant enzymes (CAT, SOD, GR, GPx) declined concentration-dependently.

How the study worked

Human undifferentiated SH-SY5Y neuroblastoma cells were exposed to THC at four concentrations (0.66, 20, 73.75, 150 ng/mL) reflecting real-world blood levels found in drivers involved in traffic accidents. Cell viability, ROS, glutathione balance, lipid peroxidation, antioxidant enzyme activities, nuclear morphology, and mitochondrial membrane potential were assessed.

What this study cannot tell us

Undifferentiated neuroblastoma cells are not identical to mature neurons. In vitro exposure does not account for blood-brain barrier, metabolism, or protein binding. The concentrations were tested as steady-state exposures, whereas in vivo THC levels fluctuate rapidly. Short exposure times may not reflect chronic use patterns.

How to read the evidence

In vitro cell study using traffic accident-relevant concentrations, limited by the gap between cell culture and in vivo brain exposure.

When this study was published

Published in 2026.

The bigger picture

The dose-dependent nature of the toxicity aligns with the potency concerns raised by other studies in this database. As cannabis products become more potent, users may achieve higher blood THC levels, potentially reaching the neurotoxic concentrations identified here. This has implications for both driving safety and long-term brain health.

Questions still open

Do these neurotoxic effects occur in actual brain tissue at achievable THC concentrations? Is the oxidative stress reversible after THC clears? Would chronic low-level exposure produce cumulative damage?

Common questions

Are these THC levels realistic?

Yes. The concentrations were specifically chosen to match blood THC levels found in drivers involved in real traffic accidents, making them directly relevant to real-world exposure scenarios.

Does this mean cannabis kills brain cells?

In a lab dish, high THC concentrations caused neuronal cell damage and death. Whether this occurs in the actual brain is not yet established, as the blood-brain barrier, metabolism, and other protective factors are not captured in cell culture models.

Read the original research

Evaluation of THC-induced neurotoxicity via oxidative stress in undifferentiated SH-SY5Y cells.

Environmental toxicology and pharmacology, 121, 104891

View on PubMed ↗Publisher’s paper ↗

Citation

Sanz-Pérez, A; Anaya, B J; Fraguas-Sánchez, A I; Serrano, D R; Pérez, T; Basilicata, P; Pieri, M; González-Burgos, E. (2026). Evaluation of THC-induced neurotoxicity via oxidative stress in undifferentiated SH-SY5Y cells.. Environmental toxicology and pharmacology, 121, 104891. https://doi.org/10.1016/j.etap.2025.104891