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Key points
- About half of the differences between people in how likely they are to develop addiction lie in their genes.
- Addiction susceptibility is influenced by externalizing, internalizing, and drug response pathways.
- Externalizing, which is related to self-regulation, is the biggest genetically influenced risk pathway.
About 1 in 5 individuals develop a substance use disorder; more than 46 million people in the United States are affected at any given time.
And yet, most people choose to use alcohol or other drugs recreationally. According to the latest National Survey of Alcohol and Health, about 85% of people report using alcohol in their lifetime. Even while evidence mounts for the harmful effects of alcohol and we continue to experience tragic fallout from the opioid epidemic, as a society we are moving toward increasing legalization and availability of drugs, including marijuana and, more recently, psilocybin.
Against this backdrop of ready availability and widespread interest in recreational alcohol and other drug use, it would be eminently helpful for people to know if they are at elevated risk for developing problems, so they could make the best choices for promoting their health and well-being.
About half of the reason some people are more at risk of developing problems with addiction lies in their genes. The other half lies in environments and experiences—things like trauma, unstable housing or employment, easy access to drugs, and being surrounded by substance-using peers.
There are three big pathways of genetic risk for addiction: (1) the externalizing pathway, (2) the internalizing pathway, and (3) drug response.
The most common misconception is that genes influence risk for addiction through the third pathway: the way our bodies respond to a drug. Yes, it is true that there are some genes that impact physiological responses to specific drugs. For example, there are genes that influence the metabolism of alcohol that make some people feel sick when they drink alcohol. Other genes influence how our bodies metabolize nicotine or respond to opioids. Whether you find a drug adverse or pleasurable naturally affects your likelihood of continued use, which impacts your chance of developing problems. However, there are only a handful of genes that influence drug response, and other than for those individuals who carry genetic variants that make them sick when they use a specific drug (which is very protective against developing problems), drug response is just one small part of genetic risk for addiction.
The bigger reason our genes influence our risk for addiction is not found in the way our bodies respond to a drug; it is found in the way our brains are wired.
Pathway #1, Externalizing, is the big one. Externalizing is a psychology term that refers to a spectrum of behaviors and disorders related to self-regulation. People who are higher on Externalizing have brains that place greater value on immediate rewards; the here-and-now is more important than possible long-term consequences or future payoffs. Externalizing can show up as risk-taking, sensation-seeking, or impulsivity. It is highly heritable, meaning that some people have brains that are naturally wired to be higher on externalizing traits. In children, it can show up as impulsivity, ADHD or other behavior problems. In adolescents and adults, it can lead to substance use problems, or other addictive behaviors, like compulsive gambling, eating, or risky sexual behaviors. In this way, externalizing risk is not specific to alcohol or any other drug; it elevates risk for all forms of substance use and for other behavioral addictions too. Externalizing is so-called because it reflects how our brains influence the way we interact with the external world.
In contrast, internalizing refers to how our brains influence our internal worlds—our thoughts and feelings, the ruminating we do inside our heads. People who are higher on Internalizing have brains that are prone toward worry and are more likely to struggle with depression and anxiety. Internalizing leads to an elevated risk of developing substance use problems when alcohol or other drugs are used to cope with or manage those feelings. For this reason, people who are higher on internalizing are more likely to drink or use drugs by themselves or as a “social lubricant” to reduce social anxiety before spending time with others.
Of the three genetically influenced pathways, externalizing is the most important at the population level—meaning that it accounts for the biggest reason why some people are more at risk of developing substance use problems. People who are higher on externalizing often start using alcohol or other drugs at a younger age because they are more sensation-seeking and eager to try new and exciting experiences. They seek out the company of other risk-taking peers, who then provide access and acceptance of substance use, creating a feedback loop of escalating risk behavior. This is why the average age of onset of developing substance use problems is in the early 20s. In contrast, people with Internalizing genetic risk tend to develop substance use problems later in life.
The externalizing, internalizing, and drug response pathways are not mutually exclusive, meaning that you can carry genetic risk across one or more pathways. Obviously, the more risk factors a person carries, the more likely they are to develop problems.
DNA is not destiny
By understanding what genetic risk factors you carry—which is purely the luck of the draw when it comes to the genes you inherited—you can also take steps to reduce risk. Some children with parents with substance use disorders already choose to do this: knowing that having a parent with problems means they are also more likely to carry genetic risk, they choose not to use alcohol or other drugs, to avoid the possibility of developing problems altogether. By taking action to change their environment, they essentially trump their genetic risk.
Many genetically influenced characteristics that increase the risk for substance problems aren’t necessarily bad things, per se. There is good and not-so-good associated with all of our characteristics. Risk-taking is associated with elevated levels of substance use problems, but entrepreneurs, fighter pilots, and CEOs also tend to be higher in risk-taking. Anxiety can cause challenges if it becomes overwhelming, but in small amounts, it can enhance motivation to prepare in advance—a good thing when prepping for tests, travel, job interviews, or sports.
The bottom line: we all have brains that are wired differently. In the same way that we can look around our world and see genetically influenced differences between us—differences in eye color, hair type, skin tones, and body shapes—there are equally interesting and wonderfully diverse differences in the way our brains work. Our genes influence how the synapses in our brain connect from the earliest points in development; they lead to our natural tendencies and traits, and then the environment further shapes our brain development.
When it comes to substance use, understanding how your brain is wired, and whether you carry any of the characteristics that can lead to a higher risk of developing problems, can help you make the best choices to have a healthy relationship with alcohol and other drugs.
