Substance abuse is an incredibly complicated spectrum of cause and effect, thought and behavior, and actions and repercussions. Entire fields of study have attempted to answer the question: Are some people more predisposed toward developing an addiction than others? While it is tempting to answer “yes” or “no,” the truth of the matter is rarely that simple. Looking at the relationship between genetics and substance abuse helps us to further understand the nature of drug or alcohol addiction.
“Genetics” is a word that people may interpret to mean different things, so clarifying the proper, scientific definition of the term is important to grasp the role that genetics plays in substance abuse.
Genetics is the study of the biological process whereby a parent passes on certain genes to their children. This process is known as “heredity.” Genes are instructions on how a human being grows and develops right down to the cellular level, but with small variations (maybe as little as one percent of the overall genetic makeup). Even though an individual has two copies of each gene, one from their mother and one from their father, they will have different physical and behavioral features from their parents, even as they will inherit their parents’ eye color, skin color, etc. They may also inherit the genes that carry the risk of certain diseases or other medical conditions.
Genetics and Substance Abuse
In the study of whether a person’s genetic makeup determines whether they become substance abusers, scientists search for biological differences that make the person vulnerable to addiction. There is no science behind the idea that a relevant genetic difference will guarantee a drug or alcohol problem. The University of Utah explains that the likelihood of someone developing an addiction involves a lot of very complex factors, including factors that are inherited from parents (children of alcoholics are four times more likely to grow up to become alcoholics themselves) and factors that arise from the person’s environment (such as living in an abusive home, even if neither parent takes drugs or alcohol).
CNN cautions that the erroneous belief that a genetic variation is a one-to-one correlation with alcoholism may give people a misguided sense of confidence in their abilities to consume alcohol, believing that since there is no known case of addiction in their family history, they can drink with impunity.
It may even be possible that in the same way that a combination of genes and environmental factors can add to the susceptibility of a person becoming dependent on drugs, those same factors may even cancel each other out, lowering the possibility that that person goes on to have substance abuse problems. This is a key reason why people’s bodies react very differently to the effects of drugs and alcohol – some may be hooked on their first shot or smoke, while some people can knock back drink after drink before showing any signs of a problem.
Instant Dependence and Neuroadaptation
The difference between intentional drug and alcohol abuse and drug and alcohol abuse that is the result of chemical dependence is enormous but subtle. The Director of the Addiction Science Research and Education Center tells the University of Texas at Austin that a person who willfully abuses alcohol has the power to stop on his own, however difficult it may be, while someone who is genetically primed to be chemically dependent on alcohol will be compelled to drink himself to death.
The director says that such people experience “instant dependence,” meaning that they are so genetically predisposed that the only way to truly avoid becoming alcoholics is to completely steer clear of alcohol and the environments, situations, and other triggers that might encourage or promote alcohol use.
On the other side of “instant dependence” is “neuroadaptation,” where the brain gradually adapts to the constant and repeated presence of the drug, to the point where trying to undo the chemical changes caused by the drug is painful and dangerous (manifesting in the form of withdrawal symptoms). Neuroadaptation can take place in people who have a genetic predisposition to substance abuse, but it can also happen to people who have no such issues. They consume so much alcohol or drugs that their bodies become corrupted to the point that they risk passing on any biologically induced deficiencies to their offspring.
Indeed, neuroadaptation itself may come down to genetic factors. Genes responsible for the development of personality characteristics, mental health, and physiological reactions to the presence of drugs and alcohol in a system (such as hangovers and impulsive behavior) can similarly influence (but not cause) neuroadaptation in the same way that other genes can influence (but not cause) instant dependence.
Inheriting an Addiction vs. Inheriting Susceptibility
All this is to point out that there is no “X marks the spot” in someone’s genetic fingerprint that will point to a future substance abuse problem. “No one,” says the University of Utah, “is born with an addiction.” However, it would be much more accurate to say that addiction is certainly influenced by genes, and that makes all the difference in the world.
The National Institute on Alcohol Abuse and Alcoholism states that genetics only account for about 50 percent of the chance of alcoholism (the National Institute on Drug Abuse says the figure ranges from 40 to 60 percent). Therein lies one of the key components of the intersection between genetics and substance abuse: A person does not inherit an addiction, they inherit a susceptibility to an addiction. It is entirely possible that someone with alcoholic or drug-dependent parents may never have that problem of his own, if he avoids the other factors of an addiction. Someone who does not have a genetic predisposition towards substance abuse can nonetheless develop a drug or alcohol habit, and the genetic changes caused by that habit may be passed down to children or descendants – who themselves will have a 50 percent chance of becoming drug addicts.
Genes, Substance Abuse and Mental Health
Furthermore, even as some genes directly impact the risks of becoming an alcoholic or drug use (either by raising or lowering them), other genes impact other factors that may eventually be associated with substance abuse, such as the following mental health conditions:
Summing up this point, the National Institute on Drug Abuse says that pre-existing vulnerabilities in genetics can put an individual at risk for both an addiction and co-occurring mental health disorders or make them susceptible for developing a second disorder after an initial disorder develops.
The Influence of Genes
Sometimes, it’s not just the genes a person has that can make them vulnerable to becoming a drug user or an alcoholic – it could be the genes they don’t have. While genes are not responsible for behavior, they are responsible for the development or functions of various systems in the body. If a gene is not present, that deficiency affects the system the gene was intended to control. In some cases, this effect is obvious, as in intellectual disability. In other cases, the effect could be much more subtle, like a long-term behavioral liability that only comes to light when the individual is older and confronted by situations and triggers that make them respond in a certain manner. A research monograph published by the National Institute on Drug Abuse clarifies that particular genes (or the lack thereof) influence a number of mental health disorders and impulsive and compulsive behaviors, like the consumption of drugs and alcohol as a go-to method of relief and control from stressful and challenging situations.
The monograph reminds readers that no gene (or one set of genes) will directly lead to a person abusing drugs or alcohol. Instead, genes determine the likelihood of such a problem developing, especially when other risk factors are taken into consideration.
The National Council on Alcoholism and Drug Dependence picks up on that train of thought, explaining that the role of genetics in substance abuse comes into play once a person actually starts abusing controlled substances. For that reason, NCADD declares as a fact that the “single most reliable indicator” of whether or not a person starts to take drugs or alcohol is family history.
The conclusive research of the effects of a family history of alcoholism is in part why some people opt not to expose themselves to any risk and eschew alcohol totally. Such is the case with Joe Biden, the 47th Vice President of the United States, who explained his lifelong teetotalism as a result of “too many alcoholics in [his] family.”
The American Psychological Association puts it quite clearly: “Genes matter in addiction,” and understanding in what ways they matter (and in what ways they don’t) is critical to devising methods of education, treatment, and prevention of substance abuse disorders. This may expand to the field of brain imaging, where the structures and functions of the nervous system are visually depicted for analysis and intervention, where necessary. Dr. Nora Volkow, Director of the National Institute on Drug Abuse, explained in an APA press release that brain imaging has suggested that people with a diminished number of a particular type of receptor in their brain might be in danger of developing an addiction to cocaine and heroin, and the number of such receptors is determined by their genetics.
Dr. Volkow’s example wasn’t a random one. The study of the gene in particular, the D2 subtype, is one of the most studied cases of genetic vulnerabilities.
When a person takes drugs or alcohol, the brain is artificially stimulated to produce dopamine, a neurotransmitter that is responsible for feelings of pleasure and reward in the brain. The D2 subtype responds to the presence of dopamine, so people who do not have this gene have a stronger compulsion for alcohol and will consume alcohol in larger amounts, when compared to other individuals who do have the gene. This is because people who lack the D2 gene do not feel the effects of dopamine as much as people who have the gene, so they have to drink longer and harder to achieve the same buzz.
The genetic factors of alcohol and drug abuse may not stop at just the moment of consumption. Individuals who have a history of drinking in their family may have more severe withdrawal symptoms (trembling, nausea and vomiting, muscle cramping, insomnia, etc.) if they try to stop drinking (thereby compelling them to continue drinking to self-medicate) than a drinker who has no alcoholics in her family tree. In fact, disclosing such a familial history is vitally important when an alcoholic seeks treatment, as this knowledge may influence a doctor to choose one course of therapy over another.
The Composition of a Substance Abuse Problem
It used to be thought that there were one or two main causes for a person becoming a substance abuser. Blame was usually placed at the drinkers’ feet: accusing them of being of weak moral character (especially with regards to women, either believing that they were more prone to being alcoholics, or that it was their responsibility to shoulder the burden of their husbands’ alcoholism), for example, or belonging to a particular ethnicity (people of Irish descent are commonly thought of as being alcoholically inclined by nature).,
Today, we know that there are many possible reasons why someone might develop a drinking problem. While genetic factors can account for roughly half the risk, the other half is spread out over a number of other concerns. As listed by the Betty Ford Center, they are:
- Gender: Men are more likely to become alcoholics than women, but women have more unique risk factors.
- Psychological factors: These include stress, depression and suicidal thoughts, among others.
- Emotional measures: People who are mentally or emotionally distressed may use alcohol or drugs to self-medicate.
- Frequency: Men who consume alcohol more than 15 times a week, and women who consume alcohol more than 12 times a week, will frequently develop a dependence.
- Social factors: The culture of alcohol may tip someone over the threshold between responsible alcohol use and problematic drinking.
Genetics is a complicated subject, and people not familiar with the basics might jump to one conclusion or another on how hereditary factors affect the likelihood of a drug or alcohol problem. While the full scope of the relationship may never be explicitly mapped out, we know enough today to say that having a parent with a substance abuse problem is not a guarantee of a future substance abuse problem, but we also know that having a parent with a substance abuse problem brings that danger much closer to home.
 “Distilling Fact from Fiction: Scientist Debunks Myths About Alcohol Dependence to Reduce Stigma of Complex Disease.” (April 2006). The University of Texas at Austin. Accessed April 30, 2015.
 “Addiction Science: From Molecules to Managed care.” (July 2008). National Institute of Drug Abuse. Accessed April 30, 2015.
 “Psychosis Susceptibility Gene ZNF804A and Cognitive Performance in Schizophrenia.” (July 2010). Archives of General Psychiatry. Accessed April 29, 2015.
 “A Common Genetic Predisposition to Stress Sensitivity and Stress-Induced Nicotine Craving.” (January 2008). Biological Psychiatry. Accessed April 29, 2015.
 “DrugFacts: Comorbidity: Addiction and Other Mental Disorders.” (March 2011). National Institute on Drug Abuse. Accessed April 29, 2015.
 “Upregulation of Cannabinoid Type 1 Receptors in Dopamine D2 Receptor Knockout Mice is Reversed by Chronic Forced Ethanol Consumption.” (January 2011). Alcoholism: Clinical and Experimental Research. Accessed April 30, 2015.
 “Alcohol-Related Sexual Assault: A Common Problem Among College Students.” (September 2005). National Institute of Alcohol Abuse and Alcoholism. Accessed April 30, 2015.