Fear can be transferred from parents to children and grandchildren, claim U.S. researchers in their article published in the journal Nature Neuroscience.
A scientific group of the Department of Psychiatry, Emory University in Atlanta, led by Dr. Brian Dias, conducted experiments on mice and found that a traumatic event can leave an imprint in the DNA of sperm, which in turn can transfer phobia and thus affect the brain structure and behavior of future generations even if they have not experienced the same painful event.
The experts believe that their discovery is important for the research and treatment of human phobias and post-traumatic and anxiety disorders through interfering with the mechanism of memory of the patients.
Specifically, using a mild electric shock, the experts trained mice to avoid the smell of acetophenone. Subsequently, it was found that the animals passed this aversion to the second next generation, although their offspring were fully isolated and had never encountered this smell before. Therefore, the negative feeling was “innate”, i.e. a product of biological memory. The negative reaction of “grandchildren” was approximately 200 % stronger against the particular stimulus, compared to other mice whose ancestors were not exposed to the same smell.
The transmitting of a phobic behavior occurs via chemical-genetic changes that alter the susceptibility of the nervous system of both progenitors and progeny, so that each next generation reacts in a similar manner to the phobic stimulus itself.
The exact biological mechanism is not yet fully understood. The most likely – in the case of lab animals – is that a chemical fingerprint of the odious smell remained in their blood and affected sperm production or, alternatively, that their brain sent a chemical signal in the sperm to change its DNA in a corresponding way.
The researchers believe that the new research provides evidence that applies to the so-called “transgenerational epigenetic inheritance“, according to which environmental factors can affect the genetic material of an individual and this effect can be inherited by offspring.
According to Professor of Psychiatry Kerry Ressler, from an evolutionary standpoint, “This transfer of information can be an effective way for parents to “inform” the subsequent generations on the importance of certain characteristics of the environment which they are likely to encounter in the future.”
Marcus Pembrey, Professor of genetics at University of London, said that “it’s time for researchers in the field of public health to take seriously human intergenerational reactions. A complete understanding of neuropsychiatric disorders, obesity, diabetes and metabolic problems is no longer possible without a transgenerational approach.”
Of course, one of the questions to answer is how many generations keep biological memory of ancestors and whether, at some point, it stabilizes through permanent changes in the genes of the offspring.