One widely cited example is from the study of Holocaust survivors and their children:

Yehuda, R. et al. (2016): Holocaust Exposure Induced Intergenerational Effects on FKBP5 Methylation. Biological Psychiatry, 80(5), 372–380.
➤ https://doi.org/10.1016/j.biopsych.2015.08.005

Another foundational study:

Meaney, M.J., Szyf, M. et al. (2004): Epigenetic programming by maternal behavior. Nature Neuroscience, 7, 847–854.
➤ https://doi.org/10.1038/nn1276

Though done in rats, this research demonstrated how early life stress—via maternal neglect—affected gene expression in offspring and influenced long-term stress reactivity.

This doesn’t mean trauma changes the DNA sequence itself. It changes how genes are expressed—which genes get activated or silenced—often via methylation or histone modification. These epigenetic changes can be passed down, especially if the stress exposure occurs during critical developmental windows (like gestation or early childhood).

Hope that helps clarify where the science currently stands. It’s not speculation—it’s measurable.