Genetics and Addiction

Genetics and Addiction Overview

Addiction is highly complex and can be associated with environmental and genetic factors. Often, whether behavioral- or substance-driven, addictions are chronic and follow a common course that includes cycles of abstinence and relapse. Genetic researchers continue to clarify the origins of addiction and whether a person’s genes may contribute to a predisposition, particularly for substance misuse and dependence. Ongoing research also seeks to identify improved therapeutic approaches, treatment response pathways, and prevention strategies. For general treatment questions, see our frequently asked questions about treatment.

Substance and Process Addictions

Characterized by compulsive, uncontrolled use of an activity or substance, addiction can lead to maladaptive and destructive outcomes if not treated. Craving, intoxication, withdrawal, and negative effects are the four primary characteristics of addiction. Both substance and process addictions have been shown to induce adaptive changes in the brain’s reward regions, leading to tolerance, habit formation, and substance- or activity-seeking compulsive behavior. Neuroadaptive changes are considered a key element in relapse. Genetic researchers attempt to determine the extent to which addiction is influenced by inherited genes and how environmental factors contribute to the development of dependency.

Genes and Addiction

It is widely accepted, based on extensive studies, that there is no single addiction gene. Rather, as with other diseases, vulnerability to addiction is complex and determined by multiple factors, including genetics and environment. That said, certain genes may combine to increase susceptibility, while others may offset one another. Not all individuals with addiction share the same genetic patterns, and not every person who carries a particular genetic variation will develop addiction. These factors make genetic research challenging, yet ongoing progress continues to show that genetic influence can play a role.

Family History of Substance Dependence

When participants in genetic studies have been asked why they avoided or used substances, many reported similar influences. Those who avoided problematic use often attributed their choices to supportive relationships or clearly defined personal goals, such as education or maintaining stable relationships. Participants who developed addiction more often cited factors such as social environment, family patterns, or personal behavioral tendencies.

It would be naive to assume that a family member’s addiction has no impact on a person’s behavior. However, contrary to popular belief, there is no single gene that causes alcoholism or drug dependence. Genetic factors may contribute, but they are not determinative. Twin studies have examined how much addiction risk, particularly alcoholism, can be attributed to genetic versus environmental factors. One study found that 48-58 percent of variation in susceptibility to alcohol dependence was linked to additive genetic factors, with the remainder attributed to environmental influences that were not necessarily shared with other family members.¹

Addiction to illegal drugs has been studied more recently in twin samples. Results suggest that genetic influence contributes between 45 and 79 percent of dependency, with the remainder being environmental.² Other studies report similar outcomes, including a 2013 twin study indicating that genetics and nonshared environments influenced alcoholism, binge eating, and compensatory behaviors, with genetic associations estimated at 38-53 percent.³

In addition to twin studies, researchers have examined large families to better understand which genes may increase susceptibility. DNA sequences of affected family members are compared with those who are unaffected to identify shared markers.⁴ Even with these comparisons, complexity remains, which is why animal studies are also used to support interpretation. Findings generally align with twin studies, suggesting genetic factors may increase vulnerability to substance dependence.

More than Genetics in Addiction

Although individuals with a family history of dependency often report higher rates of substance use, this relationship is not strictly causal. Simplifying addiction to a single explanation can obscure the broader contributing factors.

The likelihood of addiction is influenced by many interacting variables, including genetics, culture, peer environment, parenting, expectations about substance effects, physiological response, and developmental factors during early brain formation.

In addition to environmental influences, certain behavioral or mental health conditions may increase vulnerability if left unaddressed. Individuals experiencing depression, ADHD, anger, compulsive disorders, or related conditions may face elevated risk for developing an addiction. Whether these factors are inherited or acquired over time is best evaluated individually by a medical professional.

Although addiction can run in families, this does not mean individuals are destined to develop dependency. Many people possess protective coping skills that influence how challenges are managed. When addiction does occur, individuals may not control genetic background or early life factors, but they retain agency in pursuing positive change.

Research on Genetic Susceptibility to Addiction

The Collaborative Study on the Genetics of Alcoholism (COGA) is a large multistate family study initiated in the 1980s.⁵ It examines genetic factors associated with alcohol-related behaviors and risk. An updated summary is available in COGA’s recent release.⁶ Key findings include:

• Several chromosome regions (regions 1 and 7, and partially region 2) appear to contain genes associated with alcohol risk.
• A protective region on chromosome 4 near alcohol dehydrogenase (ADH) genes may reduce alcohol risk.
• Links between depression and alcoholism have been associated with chromosome regions 7 and 2.

The Texas Biomedical Research Institute studied 1,064 individuals with family histories of alcohol use.⁷ Brainwave analysis identified associations with variation in the serotonin receptor gene HTR7, suggesting correlations between serotonin activity and drinking patterns.

Born an Addict

A subset of individuals come from multigenerational patterns of addiction, prompting discussion around the concept of being “born an addict.” This term does not imply intoxication at birth, although prenatal exposure can occur. Rather, it refers to genetic and environmental predisposition toward higher risk once substance exposure occurs.

Neuroscientists emphasize two key points:

• Genetic predisposition is not destiny.
• Genes continuously interact with environmental conditions.

Environmental influences can reinforce or mitigate genetic tendencies. Supportive environments may reduce risk, while trauma exposure may increase vulnerability even without family history.

While some individuals may recognize early compulsive patterns, research has not demonstrated that a person can literally be born addicted. Risk exists on a spectrum shaped by genetics and environment.

Further Genetic Studies Related to Addictions and Behaviors

Additional studies have identified SNPs, genes, alleles, and polymorphisms associated with behavioral traits and susceptibility.

• rs53576: A SNP in the oxytocin receptor gene associated with social behavior and stress response.⁸
• rs1800497: A polymorphism of the dopamine D2 receptor gene associated with altered dopamine binding and addictive behaviors.⁹
• rs1799971(G): An allele of the mu opioid receptor gene associated with altered receptor function and potential variation in alcohol response.¹⁰

Alcoholism and SNP Genes

Several SNPs have been linked to alcohol-related behaviors and treatment response.¹¹

• GABRA2: Associated with alcohol risk dependence.
• rs27072 and rs27048: Associated with severity of withdrawal symptoms.
• rs1076565: Potential relevance in alcohol dependency development.
• rs1042173: Associated with heavier drinking patterns in some populations.

Drug Abuse and SNP Research

SNP research in drug dependency remains limited but continues to expand.

• rs135745: Associated with sensitivity to d-amphetamine effects.¹²
• rs324420: A SNP in the FAAH gene associated with increased risk of substance use behaviors.

Addiction Genes

Research continues to evaluate additional SNPs potentially associated with addiction risk.

• rs1534891: Associated with bipolar disorder and substance-related patterns.¹³
• rs686: Associated with dopamine receptor signaling and behavioral traits.¹⁴
• rs1076560: Associated with dopamine receptor function and substance response variability.¹⁵

See also the SNPedia Addiction category for SNPs related to addiction.

Conclusion

There is no single addiction gene, and individuals are not born addicted. However, genetic markers may contribute to vulnerability when combined with environmental and behavioral factors. Ongoing research within the addiction community hope to discover additional approaches that align with emerging evidence.

Sources:

1. Genetic and Environmental Contributions to Alcohol Abuse and Dependence in a Population-Based Sample of Male Twins ↩
2. The Genetics of Alcohol and Other Drug Dependence ↩
3. A Twin Study of Alcohol Dependence, Binge Eating, and Compensatory Behaviors ↩
4. Genetics and Addiction ↩
5. The Collaborative Study on the Genetics of Alcoholism: Overview ↩
6. The Collaborative Study on the Genetics of Alcoholism: An Update ↩