Evidence is piling up that sensitivity to traumatic or fearful experiences can be inherited. Although most studies looking at this issue involve mice, there are clear implications that the generational transfer of specific anxieties is possible in humans as well. If this proves true it will impact our view and treatment of anxiety, addictions, depression, PTSD and other mental health issues.
The genetic inheritance of a specific sensitivity is called an epigenetic inheritance. Epigenetics refers to environmental influences that change the expression of our genes but do not alter the sequence of our DNA. So, although our DNA remains unchanged it expresses itself through the filter of its epigenetic influence.
How This Works In Mice
In a recent study, some mice were trained—with the use of electric shocks—to fear the scent of a chemical called acetophenone. Eventually, they reacted to its smell with an elevated startle response even without receiving a shock.
These acetophenone sensitive mice were bred and they birthed pups that also had a sensitivity to the odor of acetophenone. The pups exhibited a marked startle response to its smell. Mice born of parents not conditioned to fear acetophenone did not startle at its odor.
Both the sensitized parent mice and their pups developed more neurons for manufacturing the protein that detects the acetophenone smell than the control mice and their kids. Plus, brain structures meant to receive messages from those neurons were bigger than in the control mice.
The Implications for Humans
Like the mice, humans might also inherit epigenetic influences that effect their behavior. A parent who has developed a fear of public places, for instance, could pass their heightened anxiety response to the following generation. Epigenetic modifications in the parent’s receptor genes for stress hormones could be transferred down the family tree.
However, it is too early to say whether this epigenetic transfer of emotion is actually occurring. Going back to the acetophenone-fearful mice, it is not known whether the pups inherited their parent’s fear response or just an increased sensitivity to the acetophenone scent.
What researchers hope to discover next is whether the offspring of mice who have unlearned their fear of acetophenone will also be free from the sensitivity.
Sources: Brain and Behavior