What is intergenerational trauma?

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Intergenerational trauma is the transmission of the psychological, physiological, and behavioral effects of traumatic experience from one generation to the next, through epigenetic mechanisms, altered parenting patterns, disrupted attachment, and the implicit transmission of traumatic memory through family systems and cultural narratives. The biological mechanism of intergenerational trauma transmission was first demonstrated systematically by Dr. Rachel Yehuda at Mount Sinai School of Medicine in her research with Holocaust survivors and their offspring. Her studies found that the children of Holocaust survivors showed altered cortisol levels and HPA axis reactivity compared to controls, even though they had not personally experienced the Holocaust. This was among the first empirical evidence that trauma could alter biological regulatory systems in ways that influenced the next generation. Epigenetics provides the molecular mechanism: environmental experiences, including trauma, can alter gene expression through chemical modifications to DNA and its associated proteins, without changing the underlying genetic sequence. These epigenetic modifications can be inherited. Dr. Michael Meaney at McGill University demonstrated in animal studies that maternal behavior, specifically the quality of early care, produced epigenetic modifications to stress reactivity genes in offspring that were transmitted to grandoffspring, providing a model for how early relational experience alters biology across generations. Psychological transmission operates alongside biological transmission. Traumatized parents often experience altered emotional availability, hypervigilance, intrusive symptoms, and disrupted attachment behaviors that directly affect child development. A parent who is chronically hypervigilant may transmit a threat-saturated worldview to their child. A parent who is emotionally shutdown in the freeze response may produce the attachment disruptions that generate insecure or disorganized attachment in the child. The child experiences these parental states through the only lens available: as reflecting something true about the world and about themselves. Research by Dr. Transmission Kellermann has mapped the multiple pathways of intergenerational trauma transmission, identifying at least four: epigenetic inheritance of altered stress reactivity, psychological transmission through disturbed parent-child interactions, socialization into a worldview shaped by trauma, and the living with family myths, silences, and narratives organized around unprocessed collective loss. Healing requires addressing all of these pathways: the biological through somatic and nervous system work, the psychological through relational and attachment repair, and the collective through narrative and cultural integration.