Why is it that some people can consume alcohol or drugs and never become addicted, while others are not so fortunate? You may have heard the saying, “addiction runs in families.” Is it true that genetics and addiction are linked?

Genetics and Addiction

Over the years, researchers have reviewed potential correlations that might impact the possibility of an “addiction gene.”

Researchers want to understand why some people are more vulnerable to addiction than others. Such information could be highly beneficial for developing targeted prevention strategies and more customized treatments and medications.

Additionally, there’s a desire to destigmatize addiction. Though the choice to start using drugs or alcohol is typically voluntary, it is generally no longer in one’s control once an addiction begins. Finding a link between genetics and addiction validates the idea that addiction is involuntary, and one cannot simply choose to stop using.

Genetics and Addiction Statistics

Experts have defined addiction as moderate to highly heritable, meaning that it’s transmissible from parent to offspring. According to an earlier report by the National Institute on Drug Abuse (NIDA), scientists estimate that 40 to 60 percent of a person’s vulnerability to addiction is due to genetics.

But much like other complex diseases, genes are only part of the equation. Addiction is also strongly influenced by lifestyle and environmental factors.

Our choices, our environment, even our stress levels affect us at a molecular level. These factors can leave “imprints” on our DNA, thereby changing our gene activity and expression regulation. This is known as epigenetics.

The prefix “epi-” means upon, above, or in addition to. As explained by Dr. Maria Mavrikaki, “practically, epigenetic changes are information that is added on to already existing genetic material, but can affect the expression of genes.”

Genetics and Addiction Studies

In genetics and addiction studies, statistics have shown that hallucinogen addiction is least heritable (0.39). At the same time, cocaine is most heritable (0.72.) Heritability is measured from zero to one and demonstrates how much one’s genes affect one’s traits.

Think of heritability as a line graph where zero equals environmental factors, and one equals genetics. A score close to zero indicates that almost all the variability in a trait is due to environmental factors. For example, the language spoken would have a heritability of zero.

It is important to note that this is not a percentage indicating one’s chance of addiction. Nor does it show what percentage is due to genetics compared to the environment. Instead, this demonstrates that 72% of the variability in the trait for cocaine addictions in a population is due to genetic differences among people.

Relationships Matter

Genetics and addiction studies of families adopted individuals, and twins, have also shown that an individual’s propensity for addiction “tends to be proportional to the degree of genetic relationship to an addicted relative.” Irrespective of environmental and lifestyle factors, a biological child of an alcoholic will have a higher chance of becoming an alcoholic than an adopted child. As for the situation of fraternal twins, the twin with the closer genetic makeup to their addicted parent will be more susceptible to addiction.

Age Isn’t Just a Number.

As an individual begins to age, there is a shift from environmental to genetic factors affecting addiction. According to the Virginia Twin Study, nicotine, alcohol, and cannabis use in adolescence are more likely to be attributed to familial and social aspects. However, during young and middle adulthood, these factors become less critical, and genetics become the primary influencer. Genetic factors do decline slightly as an individual continues to age.

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