What Causes Addiction?

Please check out the incredible research by leading research scientist, Dr. Danielle Dickin her white-paper: “What Causes Addiction?”

What causes addiction?Danielle M. Dick, Ph.D. 

As a researcher who runs an institute focused on substance use and mental health, this is a question that I am asked often. I’ve spent the last 20 years of my career workingon that very complex question. There’s no easy answer, as each person with a substanceuse disorder – be it problems with alcohol or opioids or any of the other drugs of abuse –has their own unique story. But we have learned a lot in the last 20 years, and one of thethings that is clear is that we’re not all equally at risk. We’re all born with our own uniqueDNA sequence, that codes for things like brown eyes or blue, but more importantly, codesfor the way our brains are wired. The way our brains are wired impacts our thoughts, feelings,and personality. That, in turn, influences the way we move through the world, which influencesour health outcomes – impacting the likelihood that we will develop everything fromcardiovascular disease to cancers to substance use problems. 

I study these pathways of risk as they relate to addiction: how we go from a baby with aDNA code to a person with a substance use disorder. It turns out there are three overarchinggenetically-influenced developmental pathways that influence risk for substance use disorders.The first of these pathways is called the Externalizing Pathway – which refers to being highlyengaged with the external world. Some of us are born with brains that are wired for sensation-seeking, for impulsivity, for action. We’re quicker to respond, and slower to think through theconsequences of those actions. Our brains are highly attuned to reward, to instant gratification,to seizing the moment and making the most out of it. These aren’t necessarily bad things -entrepreneurs, CEOs, fighter pilots are all higher on risk-taking. But these tendencies canalso get us into trouble. They can lead us to put ourselves into risky situations with substances,which can have adverse consequences – cycles of partying and missing out on other thingsthat could bring us joy, like school or work; unwanted sexual encounters; legal consequences.And the more that we heavily use substances, the drugs themselves start to further alter ourbrains, creating a compulsive cycle of seeking the drug for pleasure, replacing the normalactivities that used to bring us pleasure like friends, family, and relationships. People withexternalizing traits are more likely to experiment with alcohol or other drugs in adolescence,and when they develop problems, are more likely to develop them at a younger age. 

The second major risk pathway is called the Internalizing Pathway – which refers to our owninternal worlds. Some of us are much more attuned to our own internal dialogues and feelings.While this can be a good thing – creating empathy and making us more attuned to others’ feelings –it can also lead to depression and anxiety. Some people have brains that are wired to be more fearful,more prone to distress and negative thinking. They are naturally disposed to be glass half emptypeople, worrying about the consequences, assuming the worst. When an acquaintance passesthem on the street and doesn’t say hello, they take that as indication that the person doesn’t likethem, and extrapolate to believe that they are unlikeable, will never have close friends, aredestined to be lonely. Of course, there’s an alternative explanation: maybe that person on thestreet just didn’t see them. But people predisposed to internalizing assume the worst. This tendencycan lead to substance use as a means to cope. Interestingly, people with internalizing traitsare actually less likely (as a group) to experiment with alcoholand other drugs in adolescence than people who are high on externalizing. This is becauseadolescents with anxiety and depression are generally less connected with their peers andless likely to be at parties where alcohol or other drugs are present. A lot of substance use inadolescence and young adulthood is social. However, as a group, people with externalizingcharacteristics are more likely to mature out of risky substance use patterns after emergingadulthood, whereas people who are higher on internalizing are more likely to develop problemswith alcohol or other drugs as they age. Without strong coping skills, people with internalizingtraits are more likely to increasingly turn to alcohol once it is readily available in adulthood(and no longer as dependent on peer groups) and to use substances to deal with life’s mountingstressors. 

The third genetically influenced pathway that impacts our propensity for substance problemsis found in our Physiology. Our bodies differ in the way that we process drugs. These differencescan lead some people to be more or less likely to develop problems with that drug. For example,there are genes involved in alcohol metabolism that alter the likelihood of developing an alcoholuse disorder. Alcohol is broken down in the body into a by-product called acetaldehyde, which isfurther broken down into acetate, which can then be eliminated from the body. Acetaldehyde iscarcinogenic and causes nasty side-effects when in the body. For most of us, it is broken downpretty quickly. But some people carry genetic variants that code for enzymes that are very inefficientat breaking down acetaldehyde. This can lead to facial flushing and feelings of nausea. Whendrinking makes you sick, it turns out that you don’t want to do it very often, so individuals who carrythese genetic variants are much less likely to develop alcohol problems. These genetic variants arefound almost exclusively in individuals of East Asian descent. Other genetic variants cause peopleto more quickly breakdown alcohol into acetaldehyde; although the nasty side-effects aren’t quiteas strong, these variants are also protective against developing problems. Other genetic variantsinfluence our sensitivity to alcohol – how much we need to drink before we feel the effects of alcohol,effects that range from feeling a buzz to slurring speech. People who have reduced sensitivity toalcohol have to drink more to get the same effects; this can lead to heavy drinking patterns andput them at elevated risk for developing problems. It’s likely that there are genes involved indifferential response to many different drugs of abuse that alter an individual’s risk for particulartypes of drug dependence. 

When it comes to our Physiology until we have identified all the genes involved in drug responseand have a test for them, we don’t know what our risk is until we try a drug. That’s a big gamble.But it turns out that Physiology is the smallest piece of an individual’s potential for developinga substance use problem. The biggest factors impacting risk for addiction aren’t found in ourPhysiology, they are related to where we fall on Externalizing and Internalizing characteristics.And here’s the great thing about that: externalizing and internalizing traits don’t just show up inadulthood and suddenly impart risk. Remember that they are coded in our genes, related tothe ways our brains are wired, so Externalizing and Internalizing traits show up early in development. Temperament starts to solidify around age 3, meaning that behavior at age3 is predictive of behavior in adolescence, which is predictive of behavior in adulthood.Not perfectly of course; but it’s more than you’d expect by chance. More anxious toddlersand small children grow up to be more anxious adults. More impulsive children growup to be more impulsive adults. Our research has found that mother’s reports of their children’sbehavior prior to age 5 is predictive of whether their children will be drinking in adolescence.The child who is hanging from the top of tall trees at 5 is more likely to be the one doingbeer-bongs at 25. 

In a sense this is great news, because it means that we know who is most at risk from an earlyage and importantly, we also know that the people who are most at risk are also more likely tobenefit from prevention. Genes aren’t destiny. They only make us more or less at risk. Andunderstanding your make-up (or if you’re a parent, your child’s make-up) can help you makethe best choices for you (or your child) and be aware of natural challenges and potential pitfalls.We all have them, and they are all different, so knowing what yours are can help you tackle them.It can help you redirect those tendencies and channel them for good. The first part of slaying thedragon is realizing it’s there. There are effective research-based skills for managing depression,anxiety, and impulsivity. Learning these skills – especially early on before problems develop –can reduce the likelihood that we will develop problems, even if we are carrying a geneticpredisposition that may put us more at risk. 

Another big take-away from the past 20 years of research is that we are all products of ourgenes and our environments. There is no “nature versus nurture”; it is always both. DNAsequences in the lab do not spontaneously generate human beings; an environment isalways necessary – and can change how that DNA sequence grows. Conversely, we’renot blank slates, molded purely by our environments. Any parent with more than one childknows that – you can provide the same environment and children still turn out very differentlydepending on their own unique genetic make-ups. When it comes to substance use disorders,we know that environments can play a big role in increasing or decreasing the likelihood thatindividuals with risky predispositions will go on to develop problems. Environments where thereis little parental oversight in adolescence, or high affiliation with deviant or substance-use peerscan be particularly risky for adolescents who are high on externalizing traits. Life stressors can beparticularly risky for individuals who are high on internalizing traits. Conversely, environments likehealthy romantic relationships can be protective and reduce risk, which can be particularlyimportant for those who carry risky predispositions. 

The bottom line: we’re all at risk for something, and some of us are more likely to be at risk fordeveloping substance use problems. But the things that put us at risk for substance use problemsshow up early, which means we can identify them, work on them, and in doing so, be the mastersof our own destiny.