Fear can modify our DNA and influence the behavior of future generations, researchers find. According to a Nature Neuroscience study, when an ancestor endured a terrifying experience – and managed to survive – their genetic machinery kept note of it, manifesting as a phobia that gets passed down to subsequent kin.

To show this, researchers exposed mice to the smell of cherry-blossom in a panic-inducing situation. The so-called odor fear conditioning makes the mouse associate the cherry-blossom smell with a traumatic event to the point that a fear response occurs when they encounter the odor on its own. When female mice acquired this form of PTSD (post-traumatic stress disorder) before conception, the next two generations of mice still exhibited “behavioral sensitivity” towards the cherry-blossom odor despite never being exposed to it before, the authors report.

The study verified that this automatic fearful behavior was inherited rather than taught by finding that mice that were conceived via artificial insemination and fostered by mice they weren’t related to still exhibited this sensitivity to the cherry-blossom odor.

“The fact that these changes persisted after IVF, cross-fostering and across two generations is indicative of biological inheritance,” Brian Dias and Dr Kerry Ressler, researchers at Emory University, Atlanta, conclude in their study. “The second generation mice that we tested are a full and complete generation removed from the environmental perturbation of their parent; as such, our observations suggest a transgenerational phenomenon.”

By showing that an experience can genetically echo for generations validates the role of epigenetics; a process whereby gene activity, rather than genes themselves, dynamically respond to pivotal environmental changes, such as stress, diet, and toxins. These critical – and usually stressful – alterations typically act by flipping a chemical switch in our bodies that alters the course of how genes are expressed.

“Our results allow us to appreciate how the experiences of a parent, before even conceiving offspring, markedly influence both structure and function in the nervous system of subsequent generations,” the authors comment in their study. “Such a phenomenon may contribute to the etiology [cause] and potential intergenerational transmission of risk for neuropsychiatric disorders, such as phobias, anxiety, and post-traumatic stress disorder.”

Marcus Pembrey, Emeritus Professor of Paediatric Genetics, University College London, told Daily Mail that the study underscores the importance of transgenerational responses in public health. “I suspect we will not understand the rise in neuropsychiatric disorders or obesity, diabetes and metabolic disruptions generally without taking a multigenerational approach.” Others, such as Wolf Reik, Head of the Epigenetics and Chromatin Programme, Babraham Institute, caution that while the study results are certainly intriguing from a health standpoint, extrapolating animal models to humans requires a lot more understanding, according to the Daily Mail.

Source: Dias B., Ressler K. Parental olfactory experience influences behavior and neutral structure in subsequent generations. Nature Neuroscience, published online Dec. 1. doi:10.1038/nn.3594