Scientists and addiction experts have studied the link between genetics and addiction for decades. After all, why do some people become addicted to a substance after initial use while others do not? A wide variety of studies seems to suggest that a person’s risk of developing an addiction can depend on genetics. This concept has become an essential avenue of scientific research for addiction prevention and recovery.
The Definition of Genetics
Genes are the functional units of DNA that make up the biological properties of a living thing. The study of genes and hereditary characteristics is called genetics. On average, human DNA sequences are 99.9% identical. At first glance, this statistic doesn’t seem right. How can everyone be 99.9% genetically similar? Well, the 0.1% genetic variation accounts for roughly 3 million variances in about 3 billion DNA sequence base pairs. These distinctions in the DNA sequence translate to physical features like height, eye color, hair color, and race. They also account for an individual’s potential susceptibility to diseases like cystic fibrosis, Huntington’s disease, and many others— including addiction.
Isn’t Addiction a Choice?
Contrary to popular belief, addiction is not a choice. It is true that someone who uses a substance for the first time makes the active decision to do it. However, initial use only becomes an addiction if specific factors influence the person’s will to continue using. This includes psychological, sociocultural, and genetic factors.
These same factors can affect the development of other potential genetic diseases as well. For example, someone who rarely exercises and suffers from chronic stress has a higher-than-average risk of developing high blood pressure. If that person also has a family history of high blood pressure, then the risk is even higher. In this case, the person’s lifestyle influences an undesired condition. This same idea applies to those who struggle with addiction.
Addiction, just like any other disease, is complex. Its development depends on both genetics and environment. Once someone begins to use alcohol or drugs regularly, the risk of developing an addiction is much higher. This is especially true if genetics is a factor. This is why parents with substance use disorders (addictions) are statistically more likely than parents who do not use substances to have children who also develop addictions. Some scientists refer to this genetic phenomenon as the “addiction gene.”
Genetics as a Factor of Addiction
The “Addiction Gene”
Since addiction is a complex disease, pinpointing a single “addiction gene” next to impossible. Addiction is a trait as much as it is a condition, as is the case with other genetically-influenced diseases. So, there isn’t such a thing as a single “addiction gene.”
However, when researchers look for the “addiction gene,” they are actually examining a wide variety of genes to determine which biological variances could potentially be linked to addiction. So far, several notable studies have indicated that genetics can, in fact, influence addiction development.
NIDA’s Genetics Research Program
To further expand the research efforts into the “addiction gene,” the National Institute on Drug Abuse (NIDA) created the Division of Neuroscience and Behavior (DNB). This division’s mission is to explore the origins of addiction through clinical neuroscience and behavioral science. One particular branch— Genetics, Epigenetics, and Developmental Neuroscience— focuses on studying addiction through its genetic and environmental factors. The areas of addiction research that are supported by the DNB provide essential information that not only identifies the causes of addiction but also explores ways to treat it.
Many scientific researchers explore the “addiction gene” in studies and surveys involving twins. In fact, twin studies are among the most popular NIDA-supported scientific methods for exploring the link between genetics and addiction susceptibility.
In twin studies, researchers conduct interviews with pairs of twins who have grown up in the same environment surrounded by the same influences. The initial theory was that if genes really did influence addiction development, identical twins would be more likely to have the same substance abuse status. Simply put, either both twins would be using substances or both would not be using substances.
The Study of Kendler and Prescott
One team of NIDA-supported researchers conducted a particularly famous twins study at the Medical College of Virginia. The two lead researchers, Dr. Kenneth Kendler and Dr. Carol Prescott, examined the patterns of both marijuana and cocaine use among twins. This massive study involved a sample size of 1,934 twins (all female) ranging from age 22 to 62 years old. The team’s findings confirmed the long-suspected theory that genetics play a significant role in the likelihood of addiction development.
Kendler and Prescott later published their findings in a book titled “Genes, Environment, and Psychopathology: Understanding the Causes of Psychiatric and Substance Use Disorders.”
Dr. Kendler explained:
“Our research supports other studies that indicate [genetics] and social-environmental factors are influential in determining whether an individual begins using these drugs… But our findings suggest that the progression from the use of [substances] to abuse or dependence was due largely to genetic factors.”
Monozygotic Twins vs. Dizygotic Twins
Kendler’s and Prescott’s study also found that concordance rates were much higher for identical twins than for fraternal twins. Kendler explained that the difference in addiction rates between the two kinds of twins ranged anywhere from 60% to 80% for both marijuana and cocaine use.
Today, most twin studies explore this difference by involving both identical (monozygotic) twins, who share the same genetic code, and fraternal (dizygotic) twins, who do not. After the interviews, researchers compare results between monozygotic and dizygotic groups to better understand this massive gap in the potential for addiction development.
So far, several scientific investigations after the Kendler-Prescott study have conclusively determined that identical twins are, without question, significantly more likely than fraternal twins to both develop an addiction after exposure to drugs. So, while science has not yet identified one specific “addiction gene,” many different genetic and biological factors have been proven to make an individual more or less likely to develop a substance use disorder after initial use.
Environment as a Factor of Addiction
The Role of the Environment in Addiction
An individual’s health, as well as the risk of addiction development, depends on a variety of factors. However, a broad scope of research has revealed that the most accurate way to measure an individual’s health is by examining the dynamic interaction between the person’s genetics and environment.
Environmental influences have been a well-known factor of addiction for many years. Research from NIDA and the DNB has confirmed that genetics can influence how an individual responds to everything from peer pressure to exposure to addictive substances in social settings. This is what ultimately determines an individual’s susceptibility to developing an addiction. Therefore, the interaction between genetics and environments— epigenetics— places some people at higher risk for addiction development than others.
The Field of Epigenetics
Epigenetics is the study of inherited changes in gene expression. This field of study does not focus on DNA sequencing. Instead, it explores active versus inactive genes, and how the environment affects them. This is one of the major focuses of NIDA’s Division of Neuroscience and Behavior.
Certain environmental exposures— the choices that people make, for example— can impact gene function without changing the DNA sequence itself. These exposures leave “epigenetic marks,” which according to NIDA, can “affect health and even the expression of the traits passed to children.” Researchers at NIDA have also explained that “when a person uses cocaine, it can mark the DNA, increasing the production of proteins common in addiction.” This increased production of altered proteins corresponds with addictive, drug-seeking behaviors.
The field of epigenetics has been a driving force behind the advancement in addiction research for several years. By gathering data from both genetic and epigenetic studies, researchers can better determine the underlying causes (and biological consequences) of substance use disorders. This wide scope of data, along with technologic advancements, allow researchers to “single out individual genes or brain processes that may inform new prevention and treatment interventions,” according to NIDA.
The Purpose of Genetic Research
One goal of genetic research is to identify the biological causes of addiction development. The ultimate goal, however, is to use the data gathered in studies to develop better treatments and recovery programs.
Understanding the role of genetics in addiction development can help experts build better, more informed treatment options. The success of medications will always vary from person to person, depending on their genetics. Still, future tests and studies could determine which medications have the most potential for success based on an individual’s genetic profile.
Genetic Predisposition is Not Destiny
An important thing to remember about addiction is that genetics do not guarantee anything. Addiction is equal parts genetic predisposition and poor coping skills in response to environmental influences. So, the chances of developing addition even with a family history of it are roughly 50-50.
One study in particular— one of many twins studies— calculated this by examining a sample of 1,514 people comprised of both identical twins and fraternal twins. In this study, the identical twins of those with substance use disorders have an above-average risk of developing one themselves. This, however, was not a guarantee. With fraternal twins, the risk was even lower.
Based on the differences between the identical and fraternal twins, this study concluded that 50-60% of addiction risk is due to genetics alone. The other 50% is due to things like stress, discomfort, and other environmental factors. Many other studies yielded the same or very similar results.
So, while genetics do make up roughly 50% of the risk, it does not mean that people with a family history of substance use disorders are destined to develop an addiction. Ultimately, addiction is influenced by a wide variety of factors; genetics is only one of them.
Addiction Treatment Options at TTC Care
The connection between genetics and addiction is one that science has explored for many years. While researchers have proven in numerous studies that genetics do indeed contribute to the development of drug or alcohol addiction, it is not by any means the most critical factor. In reality, genetics is just one of many factors surrounding addiction. Millions of people come from families with a history of substance addiction, but not all of them develop addictions of their own.
If you or someone in your family has a substance use disorder, contact The Treatment Center Residential Addiction Care facility in Lake Worth, Florida. Our team of experienced addiction treatment professionals offers a variety of personalized treatment options to fit the needs of every individual patient in recovery. For more information, please call us at (844) 201-3136.