There is no gene or combination of genes that is linked with addiction as a trait a person is born with.
That doesn’t mean that genes are not part of the complex concoction that does result in addiction. But the genes that are correlated with addiction are genes for traits such as impulsiveness. Yet even these correlations are often weak or inconsistent. Some traits help describe an individual who will, when things get tough, tend toward addiction more than the next guy. But impulsiveness also puts you “at risk” for bungee jumping. And nobody is saying that bungee jumping is genetic.
Impulsivity is known to be correlated with inherited genetic factors. A recent study, which claims to be the largest of its kind, looked at the brain activation patterns underlying impulse control. The researchers identified multiple prefrontal brain networks involved with impulse control…which means they’re involved with its opposite – impulsivity. But each network was associated with a different style or type of impulsivity. Moreover, activation in one of these networks correlated with early drug or alcohol use, while activation in a different network correlated with ADHD symptoms. Already this shows that an individual’s particular brand of impulsivity lends itself to a different constellation of problems.
Of most interest, the pattern associated with early drug use was not a result of drug-taking but a predisposing factor. This means that a particular style of impulsivity predisposes teens to experiment with drugs or alcohol. It also predisposes them to experiment with a lot of other things, including sex, travel, motorcylces, and quite possibly bungee jumping. Notably, this particular brain pattern was not linked to any genetic variant. These adolescent brains have already grown up in their own specific environments, and brains rewire themselves with experience, day by day, week by week, year by year. In other words, these brain patterns were not preformed in the womb: they emerged over time in individual experiences. So genetic are often insubstantial to begin with, have to step aside to make room for the role of experience.
Genetics may load the gun, but it’s environment that pulls the trigger. The relations between genes and brain structures help – among many other factors – to build personality dispositions. They do not build addiction within a person. Addiction is an outcome, a result of a particular set of life experiences, a learned pattern of thought and behaviors. There are many brands of misfortune, both inside and outside our bodies, that can move us toward this outcome.