Yehuda's studies on Holocaust survivors

Rachel Yehuda’s research program at the Icahn School of Medicine at Mount Sinai (New York) constitutes the most robust evidence to date of intergenerational trauma transmission in humans. It began in the 1990s with cohorts of Holocaust survivors and extended to their directly untraumatized adult children.

**Key documented findings:** (1) survivors with PTSD exhibit **decreased basal cortisol** —contrary to what would be expected— and altered feedback response (Yehuda 1995, *American Journal of Psychiatry*); (2) the children of survivors with PTSD show a cortisol profile similar to their parents, even without having experienced the trauma themselves (Yehuda 2007); (3) there are **specific alterations in FKBP5 gene methylation** in children, linked to maternal trauma exposure (Yehuda et al. 2016, *Biological Psychiatry* 80:372-380); (4) epigenetic modifications are specific to the type of parental trauma (paternal vs. maternal) and its severity.

The work has been replicated in other traumatized populations: descendants of Cambodian genocide victims, children of war veterans with PTSD, children of victims of extreme urban violence. The general pattern holds, although there are variations according to the type of trauma and cultural context.

**Implication for the systemic approach**: these studies do not “prove” Hellinger or the Constellations method. What they do is provide robust biological evidence that the trauma of parents and grandparents can leave measurable marks in descendants who did not experience it, making clinical phenomena routinely observed by the systemic method plausible —within a scientific framework—.