When dealing with questions about addiction, one of the biggest concerns frequently raised is whether there are serious genetic factors. Clinicians often worry about overstating the relationship between addiction and genetics because it can be used as a defense, allowing an individual with a substance use disorder to put their hands up and say, “See? I can’t control it.” Those who have watched a family deal with the problem through multiple generations, however, are fully aware of why researchers wonder, “Is addiction hereditary?”
Estimates of Heritability
According to an NIH study, the heritability factors of addiction appear to land around 50 percent in terms of how much they explain the ability to become addicted to different substances or behaviors. Among illicit drugs, the indicated rates of heritability for different substance use disorders ranged from 39 percent for users of hallucinogens to 72 percent for cocaine users. The study used large cohorts of twins to analyze how much of their addictive behavior was driven by social and environmental factors versus how much was driven by genetics.
Another NIH study showed that siblings of those with substance use disorders displayed increased risks of dependency in relation to consumption of:
While the study didn’t include other substances, the fact that familial links for use disorders emerged across all four drugs that were tested makes it seem likely that similar linkages would be found for other drugs.
Across multiple studies, the drugs that we tend to think of being difficult to kick, such as cocaine, opiates and nicotine, consistently are linked to family and genetic factors. Even in cases such as hallucinogens, which appear to have lower genetic risks, the reality is that attributing as much as 39 percent of the risk of anything happening to a single factor is still deeply concerning.
Neuroreceptors, Genetics and Addiction
The human brain depends upon a large array of neuroreceptors and neurotransmitters, which are proteins in the body that code a variety of responses to different forms of stimulation, to function. Dopamine is one of the most widely cited in conversations about how addiction is hereditary because it’s a receptor that propels the human reward-seeking process. The role of dopamine has been cited in relation to a person’s want to:
- Consume food and drink
- Pursue relationships and sex
- Socialize with others
- Play games
- Do work
- Go after goals
When the human brain is stimulated by a rewarding activity, dopamine is released, ultimately reinforcing the idea in the individual’s mind that some activity was enjoyable. It’s one of the major drivers of the “let’s go again” feeling when someone gets off a ride at the amusement park. Beyond substance use disorders, it has also been cited as a culprit in relation to other addictive behaviors, including video gaming and gambling.
Dopamine receptor activity appears to be encoded in our DNA by a specific set of at least five sequences, and other aspects of processing dopamine appear to be linked to at least two additional gene sequences. Many different psychiatric disorders have also been linked to the genetic variability of dopamine in research subjects, and seemingly self-medicating behaviors have been noted in studies of laboratory rats and their consumption of alcohol.
Concerns About Other Receptors
Dopamine is far from the only neuroreceptor that researchers have associated with questions about addiction and genetics. Serotonin, widely thought of as a common regulator of sleep, appears to also play a role in drug and alcohol dependency. The sensitivity of a single class of receptors, 5-HT3, seems to be related to the risk of a person becoming dependent on a variety of substances, including alcohol, heroin and cocaine. Individuals with enhanced receptivity were much more likely than the general population to develop dependency issues.
Serotonin-driven genetic factors also may play a role in how people respond to stress and confrontation. The HTR1B gene, for example, seems to code proteins related to a slew of behaviors and biological activities, including:
- Feeling pain
- Responding aggressively
Individuals with this genetic marker may be more likely to be prescribed antidepressants or psychoactive drugs.
Some drugs bind directly to receptors. Alcohol modulates the activity of both GABA and NMDA receptors, influencing reward-seeking conduct by another avenue.
Exposure to certain drugs may have a noted retarding effect on how much a person gets a fix from a particular drug. This includes in utero exposure as one study of rats that were exposed to nicotine while pregnant showed. This means that the children of mothers who smoked during pregnancy may need to consume more nicotine than their mothers in order to get the same sense of reward from smoking.
Bouncing Back From a Session of Drug Use
One of the potentially more insidious aspects of addiction and genetics is that some people appear to inherit a better ability to repair their bodies than others. The SOD1 gene codes how well the body can handle the difficult task of repairing damaged neurons, and it has been cited by researchers as possibly contributing to the development of degenerative brain disorders like ALS. Given the number of substances that have been linked to brain damage, it’s reasonable to question whether some of the cognitive decline seen in individuals with addictions may be attributed to a genetically lowered ability for their brains to recover from heavy or repeated bouts of consumption.
The Heritability of Mental Illness
Those who exhibit signs of mental illness are about twice as likely as the general population to engage in the use of illicit substances. Research has also demonstrated that a number of types of mental illness have genetic factors. This means that in addition to the primary genetic factors for addiction, such as neuroreceptor sensitivity, there are also secondary genetic factors, including familial dispositions to mental illness. It’s likely not an accident that many people drink alcohol or consume drugs in order to attain a feeling of normalcy.
Anxiety may feature strongly in the emergence of withdrawal problems among addicted individuals. The CREB gene that played a role in the previously mentioned laboratory study of apparently self-medicating behaviors also appears to track with withdrawal difficulties and anxiety.
The uneven distribution of genetic markers for addiction-related issues across different populations suggests that distinct racial groups may be more susceptible to certain hereditary addiction patterns. One of the most widely recognized is the tendency of individuals of East Asian descent to experience the alcohol flush reaction.
It should be noted, however, that separating the noise of racial prejudice as a driving factor in addiction and its treatment from genetic factors remains a tricky proposition at best. The emergence of the opioid epidemic in primarily white communities in America, for example, has challenged some racially charged assumptions, although further research is needed. The interaction of socioeconomics, race and genetics remains extremely difficult to fully sort out as evidenced by research that showed higher rates of drug use among white college students.
Epigenetics and Addiction
Within the field of genetics, epigenetics is an old idea, once thought to be close to totally discredited, that has found new interest among researchers. The core idea behind epigenetics is that environmental influences can lead to changes in an organism that can be transmitted from parent to child. As the body of research into how gene expression works has grown, evidence has accumulated that DNA modifications can occur that don’t change how sequences are coded. This has led to further questions about what actually comes into play when we ask, “Is addiction hereditary?”
Environmental influences can cause the human body to express genes differently. Some genetic sequences are present but not activated at all until a specific environmental stress causes them to be expressed. Environmental factors that trigger gene expression include:
- Early childhood stress
- Exposure to different temperatures or amounts of light
When thinking about epigenetics and addiction, it’s easy to see the potential for highly dynamic interactions within families. A family with genetic dispositions to addiction and mental illness, for example, might provide an early childhood environment that’s stressful and impoverished. When thinking about families across several generations, the chances that addiction problems can be compounded several times may go up with each generation.
Resistance to Addiction
Between 60 and 80 percent of people in a study of individuals with substance use disorders in their teens and 20s demonstrated the ability to be completely free of drug and alcohol problems by their 30s simply because they had aged out of such behaviors. This suggests a sizable percentage of the population, possibly a majority, has a natural ability to kick drug habits with minimal to no help.
It should be noted, however, that the remaining 20 to 40 percent appeared to have significant trouble kicking drug and alcohol habits even after the majority of their friends had aged out of such behaviors. A study of the differing abilities of people to kick a notoriously difficult drug to quit, nicotine, concluded that:
- Susceptibility to addiction is about 60 percent genetic.
- Capacity to quit a drug is about 54 percent genetic.
When thinking about the overlaps of different populations and their genetic makeups, this means there are those who:
- May never get addicted and could easily beat addiction if it happened
- Can get addicted easily but can also quit with fewer challenges
- Might not easily get addicted but could have trouble kicking a habit if they did
- Are prone to addiction and will have difficulty quitting
The first thing to keep in mind is that your destiny is not coded into your DNA. Addiction and genetics do appear to be related, especially for certain sections of the population, but recovery is possible for everyone. For some individuals, stopping alcohol or drug use may be as simple as just saying no. For others, however, genetic and epigenetic factors mean they will need to approach the problem in a more structured manner.
Given what we know about the genetic predisposition to go through a difficult withdrawal process, some people absolutely need to work through a treatment program in order to move forward with their lives. This is especially the case when talking about substances like cocaine and alcohol that can lead to fatal withdrawal complications.
Recovery is a lifelong commitment for those who have use disorders along with their partners, family members and friends. Relapses can and do happen, too. The important thing is to remain supportive and stay focused on the goal of getting control of one’s life. By working with experienced professionals, even someone with the worst worries about addiction and genetics can chart a path to a better tomorrow.