This Just In: Your Genes May Inherit Your Father’s Stress Through His Sperm

A recent twist by ‘trauma creators’ is to use epigenetics to revive long-dead Lamarckian genetics.

CATEGORY: CONTROL OF LANGUAGE AND IDEAS

Jetro Tuulari, MD, PhD

Source: Molecular Psychiatry
Read time: 2.4 minutes
 
This Happened
The academic world’s long-standing romance with the idea that trauma leaves ghostly fingerprints on our very DNA has taken yet another turn—this time via the sperm cells of Finnish men. A new study in this genre found some associations with two types of epigenetic variables.
 
Who Did This?
Jetro Tuulari is an Associate Professor in the Department of Clinical Medicine, University of Turku, Finland. He has published two prior studies on trauma and eighteen prior studies on non-trauma stress. Much of his work is aimed at finding how stress during pregnancy impacts children’s brain development.
 
The Claim
There has been growing interest in the prospect that life experience—in particular, exposure to trauma and stress—can be passed on to subsequent generations through heritable epigenetic modifications, firmly planted in the lush, speculative landscape called “intergenerational transmission of trauma.” The possibility remains highly controversial, even according to some whose careers are invested in the prospect [1]. A first step in proving this claim is that epigenetic changes attributed to trauma and stress exist in sperm.
Tuulari and colleagues measured the amount of trauma exposure for each man with a self-report questionnaire. They measured epigenetic changes in sperm on two variables: (1) The number of small non-coding RNAs (sncRNA). The abundance of five broad classes of sncRNAs did not differ between high-trauma and low-trauma groups. On analyses at a narrower level, however, 29 miRNAs, 15 tsRNAs, and 3 piRNA clusters were lower, and 18 miRNAs, 6 tsRNAs, and 1 piRNA cluster were higher in high-trauma group sperm compared to low-trauma group.
(2) The amount of DNA methylation. Those with high-trauma exposure showed relatively less methylation on three regions compared to those with low trauma. That’s right—three.
 
Analysis
An online supplement reveals (if one hand-counts all their tests) that they tested 509 miRNAs, 266 tsRNAs, 509 piRNA clusters, and 541 DNA methylation sites. Out of 1,825 total tests, seventy-five tests, or 4%, were significant. One must question the random chance nature of these findings.
More importantly, did their findings replicate findings from three previous sperm studies? Overall, the researchers demurely concluded, “We found an interesting overlap with previous reports for miRNAs, particularly miR-34c-5p, although most of our results were distinct from prior reports.”

Welcome to the modern genetics game: perform thousands of tests, cherry-pick the handful that sparkle, and cross your fingers no one checks the math. Each study finds something—but rarely the same thing.

There seems to be two possible interpretations for this state of evidence.
​The Charitable View: Perhaps trauma does leave molecular breadcrumbs, but our tools are too crude to see the full picture. In addition, any true relation may have been hopelessly obscured by foolishly using self-reports of trauma exposure which have been shown empirically to be riddled with false positives [2].

The Skeptical View: There is no there there. All the findings may be spurious, caused by chance findings in small samples. The sample size of the three prior sperm studies were 28, 34, and 58 men. Tuulari et al.’s sample sizes were 30 for RNAs and 55 for DNA.
 
Why Did This Happen?
Now we come to the heart of the matter.
For decades now, a faction of ideologically-inclined scientists—let’s call them The Trauma Creators—have labored to recast virtually every social ill as the aftershock of some primordial wound. With the discovery of epigenetics, this extraordinary project expanded to an even more extraordinary newer claim that such damage is passed to generations. Their bet is that neuroscience, epigenetics, and a cascade of shimmering brain scans would someday validate their suspicion that trauma not only warps the soul but etches its sorrow into our double helix.
Scientists are allowed their wild speculations. For the time being, however, Lamarckian inheritance of trauma and stress through epigenetics remains a scientific fan fiction—highly readable, emotionally charged, and scientifically unproven.
 
 
References
[1] Nestler EJ. Transgenerational Epigenetic Contributions to Stress Responses: Fact or Fiction? PLoS Biol. 2016 Mar 25;14(3):e1002426. DOI: 10.1371/journal.pbio.1002426. Erratum in: PLoS Biol. 2016 Jun 7;14(6):e1002486. DOI: 10.1371/journal.pbio.1002486.
[2] Scheeringa MS (2025). False positives for Criterion A trauma events and PTSD symptoms with questionnaires are common in children and adolescents and could not be eliminated with enhanced instructions. Journal of Child and Adolescent Psychopharmacology, DOI: 10.1089/cap.2024.0126.