Adolescent THC Exposure in Rats Changed DNA Markers in Their Offspring's Brain Reward Center | Research

The takeaway

Rats exposed to THC during adolescence showed over 1,000 regions of altered DNA methylation in the nucleus accumbens of their unexposed offspring, many affecting genes involved in brain signaling.

Readers interested in epigenetics, how parental drug exposure might affect future generations, and adolescent cannabis use.

1,027 differentially methylated regions found in offspring never exposed to THC

What the researchers found

Researchers examined whether THC exposure during adolescence could produce epigenetic changes that pass to the next generation. They exposed adolescent rats to THC, then studied the brains of their adult offspring who were never exposed to the drug.

Using genome-wide DNA methylation profiling, they identified 1,027 differentially methylated regions (DMRs) in the nucleus accumbens, a brain region central to reward processing. These changes were found primarily in introns, exons, and intergenic regions rather than gene promoters.

Among the affected genes, researchers found a network involved in glutamatergic synapse regulation. These genes also showed altered mRNA expression, suggesting the methylation changes had functional consequences for brain signaling.

Why it matters

If adolescent drug exposure can alter gene regulation in offspring who were never themselves exposed, it adds a new dimension to understanding drug-related vulnerability across generations. The nucleus accumbens is critical for motivation and reward, making changes there particularly relevant to addiction risk.

The numbers in context

1,027 differentially methylated regions identified. 16 animals per group. DMRs were predominantly in introns, exons, and intergenic intervals, with significant depletion in gene promoters. A network of glutamatergic synapse genes showed both altered methylation and changed mRNA expression.

How the study worked

Adolescent Long-Evans rats were exposed to THC. Their unexposed F1 offspring (16 with parental THC exposure, 16 without) were studied as adults. Enhanced Reduced Representation Bisulfite Sequencing was used to profile DNA methylation across the genome in nucleus accumbens tissue. Gene expression was measured via mRNA analysis.

What this study cannot tell us

This was an animal study, and epigenetic findings in rats do not directly translate to humans. The THC doses and exposure patterns may differ from typical human adolescent use. The study examined one brain region and one generation of offspring. Whether these epigenetic changes affect actual behavior in offspring was not fully characterized.

How to read the evidence

This is an animal study examining epigenetic effects across one generation. While the findings are notable, translating epigenetic research from rats to humans involves substantial uncertainty.

When this study was published

Published in 2015. Transgenerational epigenetic research has continued to evolve, though human evidence remains limited.

The bigger picture

This research contributes to the growing field of transgenerational epigenetics, which examines how environmental exposures can affect subsequent generations through chemical modifications to DNA rather than changes to the DNA sequence itself. The findings raise questions about long-term population-level effects of adolescent cannabis use.

Questions still open

Do similar transgenerational epigenetic effects occur in humans who use cannabis during adolescence? Do these DNA methylation changes translate into altered behavior or addiction vulnerability in offspring?

Common questions

Does this mean a parent's cannabis use will affect their children's brain?

The study found epigenetic changes in rat offspring, but whether similar effects occur in humans is unknown. Human genetics, epigenetics, and exposure patterns are far more complex than those in laboratory rats.

What is DNA methylation?

DNA methylation is a chemical modification that can change how genes are expressed without altering the DNA sequence itself. It is one of several "epigenetic" mechanisms that cells use to regulate gene activity, and it can sometimes be passed from parent to offspring.

Read the original research

Genome-Wide DNA Methylation Profiling Reveals Epigenetic Changes in the Rat Nucleus Accumbens Associated With Cross-Generational Effects of Adolescent THC Exposure.

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 40(13), 2993-3005

View on PubMed ↗Publisher’s paper ↗

Citation

Watson, Corey T; Szutorisz, Henrietta; Garg, Paras; Martin, Qammarah; Landry, Joseph A; Sharp, Andrew J; Hurd, Yasmin L. (2015). Genome-Wide DNA Methylation Profiling Reveals Epigenetic Changes in the Rat Nucleus Accumbens Associated With Cross-Generational Effects of Adolescent THC Exposure.. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 40(13), 2993-3005. https://doi.org/10.1038/npp.2015.155