Genetics Provide Insight to Addiction, But No Easy Answers

The identification of genes associated with increased risk for addiction offers tremendous hope for treatment — but no solid help for clinicians or addicts quite yet.

Today, genetics provides little in the way of concrete information for physicians or for pharmaceutical companies, leaving us largely dependent on tried-and-true therapies and preventive strategies.

The lack of a magic bullet does not mean the new genetic associations have not helped clinicians in the field of addiction recovery. To the contrary, the media buzz about these developments has served a crucial role in changing perceptions of organizations that fund research, physicians, family members, and addicts.

Public awareness of the genetic underpinnings of addiction, even if misunderstood, has moved the discussion about addiction from one of moral failings or a disease of choice concept toward a more medical model. By overcoming the view that addictions are purely voluntary, the genetic research has transformed our understanding of the biological basis of addictions and, at the same time, mitigated some of the prejudice against those who have the disorders.

Identification of relevant genes or alleles has advanced the discussion further down the path begun in 1997 by Alan Leshner, who, as director of the National Institute on Drug Abuse, advocated that addiction was best understood as a chronic, relapsing brain disease. In his model, individuals initially choose to use, but then neurochemical processes in the brain made it harder to stop using, even if they were sober for an extend period.1

Adding the genetic layer to the understanding of addiction helps people to see it increasingly as just another disease. As a result, patients are more likely to seek treatment and family, friends and medical professionals are more likely to refer them for therapy to help them overcome the “compulsive and dyscontrolled use of a drug or activity, with maladaptive and destructive outcomes.”2 The sooner addicts receive treatment, the easier recovery is and the less long-term physical and emotional damage they sustain.

If, as current research shows, addictions are fundamentally like high blood pressure or diabetes, highly heritable but influenced by environment and behavior, then they — and individuals that have them — can be treated like those with other common, chronic diseases. And, like many other diseases, their biological and genetic factors can be seen as complex and interrelated.

So far, researchers have identified a number of candidate genes that may contribute to addiction. The presence of these genes or their particular mutations does not determine who will develop an addiction, but they may indicate which individuals are at greatest risk.

The genes are like the components of a good vegetable soup. Just as you could not tell me the one ingredient that makes a soup delicious, researchers cannot tell us which one gene causes addiction. You need a mix of vegetables and spices cooked for the right time at just the right temperature for the soup to taste good. For addiction to develop, you may need a specific constellation of genes, with contributing factors such as childhood trauma.

Addiction arises from a massively complex system with genetics predisposing some individuals to its development. Greater research in this area will provide a better understanding of the important factors and contribute to the development of more effective and perhaps more personalized treatments.

While we cannot simply run a genetic test to predict an individual at risk or determine the best treatment today, knowing that heredity plays a role can help clinicians identify which patients may need more support to avoid developing a substance abuse disorder or require more monitoring for risky behaviors. It makes sense to ask a patient whether addictions run in the family as we now know that individuals with first-degree relatives with substance-use disorders have an elevated risk of addictions themselves.

Family, adoption and twin studies demonstrate that risk increases proportionally with the degree of genetic relationship to a relative with an addiction. For hallucinogens, the heritability is 0.39, where for cocaine, it is 0.72. The importance of heredity increases with age. Adolescents who initiate nicotine, alcohol or cannabis use are influenced more by familial and social factors, while by middle age, genetic factors become dominant, according to the Virginia Twin Study.3

Genetics do not, however, provide an excuse to abuse substances. Addictions cannot develop in the absence of the availability of an addictive agent and the initial decision to use it, making social policy and preventive practices important. Social and familial factors largely determine the availability of addictive substances and the creation of scenarios that facilitate abuse, while genotype influences the individual’s vulnerability to addiction.

The rapidly expanding understanding of the genetics and biology of addiction will, in time, enable the development of targeted, effective therapies. In the meantime, clinicians and addicts alike benefit from the awareness that addictions share much in common with complex, chronic conditions such as diabetes, obesity and coronary heart disease. They should be diagnosed, treated, and managed for the long-term with similar strategies.

1. Hall W, Carter A, Forlini C. The brain disease model of addiction: is it supported by the evidence and has it delivered on its promises? The Lancet Psychiatry. January 2015;2(1):105-110.
2. Bevilacqua L, Goldman D. Genes and Addictions. Clin Pharmacol Ther 2009 Apr;85(4):359-361.
3. Kendler KS, Schmitt E, Aggen SH, Prescott CA. Genetic and environmental influences on alcohol, caffeine, cannabis, and nicotine use from early adolescence to middle adulthood. Arch. Gen. Psychiatry 2008;65:674–682.