Sep 25, 2014

The Interplay of Genes and Experience

Dr. Nina Sand-Loud is a Developmental-Behavioral Pediatrician at Dartmouth-Hitchcock Medical Center. She received her medical degree from McGill University Faculty of Medicine and has been in practice for 18 years. Her special interests are child development, sleep disorders, learning disorders and prematurity. Dr. Sand-Loud also serves as an Assistant Professor of Pediatrics at the Geisel School of Medicine at Dartmouth.

The Interplay of Genes and Experiences

Are our children the product of their genes or of their environment?  We had come to believe that DNA makes us who and what we are, kind of like a genetic blueprint for development. However, researchers in recent years have come to realize that genes aren’t a fixed, predetermined program simply passed on from one generation to the next.

Those in the new, cutting-edge field of “epigenetics”—studying how the expression of one’s genes can be modified by experience—are working hard to explain how we have the same genes as our parents, but may follow a different path. New findings show that the positive and negative experiences a child has—particularly during the earliest stages of life—can affect how genes work, and therefore, how children develop.

Children inherit approximately 23,000 genes from their parents, called the “structural genome.” If we’re speaking in terms of an instruction booklet for development, the structural genome is a list of all of the traits and functions that are available to be expressed over a lifetime.

The “epigenome” outlines which traits and functions should be expressed (activated and deactivated) and when.

At the time of birth, a child’s structural genome is complete. However, the epigenome is “written” over time—and the experiences a child has can influence what it says. Therefore, it’s to every child’s advantage to have experiences that will impact the epigenome in the most positive way possible—so that the child can develop the traits and functions that will allow him to reach his full potential.

Some of the factors that affect the epigenome are what we eat, how much stress we undergo and what toxins we’re exposed to—all of which add up to provide both positive and negative early experiences.

What scientists call “toxic stress” is one example of a negative influence on the epigenome. Sustained, extreme stress (such as repeated physical or emotional abuse)—without the buffering effect of a nurturing relationship with an adult caregiver—can rewrite the way a child’s body responds to stress, altering his or her ability to recover quickly from adverse situations. In this case, if the child develops a prolonged stress activation response—in which the body is flooded with cortisol for a toxic amount of time—mental and physical illness can result.

On the other hand, positive, stimulating experiences—such as “serve and return” interactions—activate the brain connections dedicated to learning and memory over and over again, resulting in the modification of the epigenome in a way that improves a child’s cognitive and social-emotional abilities.

Most alterations to the epigenome affect multiple organ systems, impacting how the brain, heart, kidneys and other organs develop and function. A child’s earliest experiences have the greatest impact on those developmental changes, influencing the child’s mental and physical health over his or her lifetime. The brain is especially sensitive during these critical years, adapting to the child’s experiences, environment and nutrition. 

Now that we know that a child’s gene expression is vulnerable to his or her earliest experiences, we should ensure that all children get the support they need during the first years to help them reach their full developmental potential. Research on the epigenome shows how external experiences impact how the brain is built, setting a child up for success or challenges. While some of the early negative changes can be reversed later in life, retroactive treatment generally requires a much greater investment of resources than getting it right the first time. 

If we want a competitive future workforce, strong future leaders, and the biggest return on our investment in our children, we must focus on the first years.

For interactive step-by-step illustrations showing how early experiences affect gene expression (developed by Harvard's Center on the Developing Child), click here.

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