Phobias May Be Inherited, Animal Study Suggests

Parents pass on their traumatic experiences to their offspring via their sperm and eggs, according to an animal study that could explain why some people seem to be born with irrational phobias.

Emory University researchers paired a mild electric shock with the a smell produced by the chemical acetophenone. They did this knowing the smell is responsible for activating a specific cell cluster in the nose and a particular "odor receptor" gene in the cells.

They then bred those mice in order to create a second generation, which showed increased sensitivity to the odor despite never having been exposed to it before. Even more stunning was the discovery of the same reaction in the third generation of mice, or grandchildren of those originally dealt the shock.

Dr. Kerry Ressler, a professor of psychiatry and behavioral sciences, and Brian Dias, the first author of the paper published in Nature Neuroscience and a postdoctoral fellow, were surprised upon further analysis to find that both the second and third generation of mice had noses with more M71 neurons, which contain a receptor capable of detecting acetophenone. Their brains also boasted larger M71 glomeruli, the area of the olfactory bubble that detects the chemical's odor.

"When Brian came in with the first set of data, we both just couldn't believe it," National Geographic quoted Ressler as saying. "I was like, 'Well, it must just be random, let's do it again.' And then it just kept working. We do a lot of behavior [experiments], but being able to see structural change that correlates with behavior is really pretty astounding."

In order to rule out the possibility that the increased sensitivity was somehow passed down from parent to child through instruction, the scientists gave a group of the offspring to other mice that then cared for them.

Still, the phenomenon remained, suggesting the changes are rooted in epigenetic alterations, or shifts in genetic expression.

Going forward, the researchers hope to uncover whether these effects are reversible and if they only occur with odors, as well as whether all sperm or eggs contain epigenetic marks affecting odor sensitivity.

"We are really just scratching the surface at this point," Dias said in a statement. "Our next goal must be to buffer descendant generations from these effects, Such interventions could form the core of a treatment to prevent the development of neuropsychiatric disorders with roots in ancestral trauma."