What is epigenetics?

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Epigenetics is the study of heritable changes in gene expression that do not involve alterations to the DNA sequence itself — changes caused by environmental influences, lived experience, and stress, which can affect which genes are switched on or off, and can be passed to subsequent generations. The word epigenetic means "above the gene." Where genetics studies the DNA code itself, epigenetics studies the molecular switches and tags — primarily methyl groups and histone modifications — that determine whether a gene is expressed or silenced. These switches are responsive to environment. Dr. Michael Meaney at McGill University demonstrated a landmark finding: the quality of maternal care in rats directly altered the epigenetic expression of stress-response genes in offspring. Rats that received more licking and grooming showed lower stress reactivity as adults — not because of DNA differences, but because of epigenetic changes triggered by care. In humans, Dr. Rachel Yehuda at Mount Sinai Hospital studied Holocaust survivors and their children. She found that both groups showed altered cortisol profiles — specifically, lower cortisol levels associated with heightened stress sensitivity — suggesting that the trauma's biological effects were transmitted to offspring who had not experienced the events themselves. The practical implication for healing: the stress patterns, threat sensitivities, and emotional regulatory difficulties a person experiences may be partly inherited from ancestors who survived violence, famine, displacement, or other severe stress. Healing oneself may literally change what is passed to the next generation.