(Nineteenth in a series of topical blogs based on chapter by chapter excerpts from Opiate Nation. Translation into most languages is available to the right.)
DNA sequences for any human is approximately 99.9 percent identical to every other human. That means that only 0.1 percent of our genetic makeup is unique to us. Genes are functional units of DNA that make up the human genome. But don’t be fooled into thinking that 0.1 percent variation is insignificant. It is nearly 3 billion base pairs of DNA which boils down to 3 million differences that determine our physical features like hair and eye color and health risks or protection from diseases such as heart disease, diabetes – and addiction. Genes influence the numbers and types of receptors in peoples’ brains, how quickly their bodies metabolize drugs, and how well they respond to different medications.
The National Institute of Drug Abuse (NIDA) reports that family studies that include identical twins, fraternal twins, adoptees, and siblings suggest that as much as half of a person’s risk of becoming addicted to nicotine, alcohol, or other drugs depends on his or her genetic makeup. Scientists estimate that genes – including the effects environmental factors have on a person’s gene expression, called epigenetics – account for between 40 and 60 percent of a person’s risk of addiction.
Epigenetics – epi meaning “above” – is the study of functional, and sometimes inherited, changes in the regulation of gene activity and expression that are not dependent on gene sequence. This means exposures or choices people make can actually “mark” (remodel) the structure of DNA at the cell level. So epigenetic regulatory systems enable the development of different cell types (e.g., skin, liver, or nerve cells) in response to the environment. These epigenetic marks can affect health and even the expression of the traits passed to children. For example, when a person uses cocaine, it can “mark” the DNA, increasing the production of proteins common in addiction which is believed to correspond with drug-seeking behaviors.
There is ongoing disagreement on whether addiction is inherited (nature) or the result of environment (nurture). But what is becoming clearer as research moves ahead is that it is nature and nurture. Environment in regard to gene expression looks at what is happening when a child is growing up with factors such as trauma, lifestyle factors (such as exercise and diet and stress), and exposure to addictive substances. Dr. Nora Volkow, director of (NIDA), tells us that early exposure to drugs greatly compounds the genetic predisposition for addiction.
For our family and many others with children who have become addicted in the past several decades to alcohol, drugs, and cigarettes, nature (genetics) played an oversized role. Our son, and every one of his friends who struggled with drug or alcohol addiction, had relatives from previous generations who were addicted to alcohol. And there is sufficient scientific evidence to support the facts of genetic tendencies for addiction.
BUT for this same generation of children, Millennials and also Gen Z’s, one component of environment has had a more pronounced influence. Our son, and the majority of his friends, did not grow up in poverty or with childhood trauma, lack of exercise, poor diet and stress. Their early exposure to addictive substances in their family would have been alcohol consumption and the prescription benzodiazepines and opioids in their parents’ medicine cabinet. But by and large the biggest environmental exposure for these young people has been the prevalence and readily available highly potent and highly addictive drugs at their schools and parties. This was not their parent’s marijuana.
What has become clear is that children from families with a genetic predisposition for addiction are more vulnerable to the heightened opportunity and availability of environmental exposure – whether it be from growing up in poverty or affluence.