by Dov Michaeli

For  Pat

How many times have you heard this refrain? It comes up as an attempt to explain quirks of personality, inappropriate behavior, even
asocial criminality. So how could a parent, long deceased, exert such long-distance influence on a 65 year old, social security and
medicare-qualified adult?

Freud theorized that we never really outgrow our childhood, that those distant traumas manifest themselves in complexes such as
the Oedipus variety. Jung spun out of whole cloth a narrative of a universal myth and sixteen archetype personalities. Modern psychologists had equally unsatisfying theories, none answering the basic question –how could parental influence last a lifetime? We use all kinds of metaphors, such as “repeating the script”(taken appropriately from the worlds of the theater, as if life is a Greek tragedy) to describe the inexorable progression through life, as if it was scripted by our parents. But how does it work?


Researchers have long suspected that such a long lasting influence of parents on their offspring’s behavior had to be genetic. Except
that a mechanism for such an influence has never been demonstrated.

Recently, the enigma has begun to be unraveled. What is at work here is a well-known phenomenon. When a methyl group is attached to a
gene, or to the chromatin that envelopes it, it acts like a light dimmer in an electric switch. It can increase or reduce the activity of the gene, not
necessarily completely switching it on or off. Such a mechanism would allow for finely tuned levels of gene expression, which in turn can result in the endless variability of behavior.

In the December 2010 issue of Cell Oliver Rando and his colleagues from the University of Massachusetts and the Hebrew University in Jerusalem described the first experiment in mammals showing the effect of parental stress on their offspring.
They found that  male rats fed a low-protein diet exhibited changes in DNA methylation and higher levels of cholesterol formation in the liver—differences that they then passed on to their young.

What about humans? A study published online (August 28, 2011) in Child Development showed that parental stress is transmitted epigenetically (namely, through methylation of the DNA) to their children. A University of British Columbia team obtained cheek swabs
from 109 adolescents. The history of these adolescents was well-documented since infancy; they were part of a study at the University of Wisconsin, in which their parents were asked to report on their stress levels, including depression, family strife, parenting issues and
financial worries. And critically, their DNA was collected and saved! Sixteen years later the Canadian investigators examined their genes and looked for patterns in methylation. Lo and behold, not only did the parents transmit patterns of methylation to the offspring, but mom and pop had different influences. Teens whose mothers reported higher stress during infancy had similar methylation patterns — affecting scores of genes including those related to anxiety levels, insulin suppression and brain development. A total of 139 genes were found to correlate with
stress levels reported by mothers.

What about a stressed father? Only 31 genes correlated with fathers who reported stress during their kids’ preschool years. Not only that: fathers’ stress was important during the child’s toddler years, not during infancy. Mother’s stress was found to be of equal influence for boys
and girls. Father’s stress influenced more girls than boys.

This is a fascinating study, whose importance transcends the narrow question of parental stress influencing their children’s gene expression. As Dr. Hertzman, an author of the study observed:

“In the past, your DNA was seen as a blueprint. It had a one-way conversation with the world. In fact, it’s a two-way conversation and the environment is telling it (i.e. your genes) how to behave.”
As if we needed more justification for providing a nurturing environment for our children, here comes the field of genetics and nails it for us.

Dov Michaeli, MD, PhD
Dov Michaeli, MD, PhD loves to write about the brain and human behavior as well as translate complicated basic science concepts into entertainment for the rest of us. He was a professor at the University of California San Francisco before leaving to enter the world of biotech. He served as the Chief Medical Officer of biotech companies, including Aphton Corporation. He also founded and served as the CEO of Madah Medica, an early stage biotech company developing products to improve post-surgical pain control. He is now retired and enjoys working out, following the stock market, travelling the world, and, of course, writing for TDWI.


  1. Is that why the Catholic Church says,”If we can get them for the first 6 years we have them for a lifetime”? Early conditioning is like the chicken pox virus. It gets in your nervous system and never leaves. You need to develop a strong sense of mindfulness. If not, early conditioning influences can run you forever.

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