What Causes Addiction: Part 1, Nature

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David Fawcett PhD

Every addict I’ve ever worked with, without fail, wants to know why he or she is addicted. Often, these individuals, early on, are more focused on the question of why they’re an addict, perhaps wanting to know who they can blame for their predicament, than on the question of what they’re going to do about the addiction. This occurs despite the fact that why a person is addicted, in the early days of treatment, is almost completely irrelevant. What matters at that point is understanding the nature of the addiction and implementing concrete actions to halt it. But still, this question is asked, sometimes repeatedly, and occasionally the addict is either unable or unwilling to move forward without an answer.

Happily, there is actually a great deal of research into the causes of addiction. What that research tells us is that there are two primary risk factors for addiction:

  1. Nature (Genetics)
  2. Nurture (Environment)

In this post I will discuss the first risk factor: nature. Next week I’ll examine the second factor: nurture.

Nature (Genetics)

Dozens of studies have demonstrated a connection between genetic makeup and addiction. The majority of this research is focused on alcohol addiction, but it is reasonable to extrapolate the findings to other addictions. The primary takeaway from this research is that various genetic differences can either increase or decrease the risk for addiction. Moreover, the genetic impact can be either direct or indirect.

Direct impact usually occurs because a genetic factor alters the ways in which a particular substance is experienced and processed in the brain and body. For example, one study found that individuals who, courtesy of their genetics, have less reactivity to alcohol (as measured by body sway) are more likely to become alcoholic.[i] Basically, individuals who are less susceptible to the side effects of alcohol can consume more (get higher) with fewer unpleasant side effects (falling down, getting sick, passing out, etc.) Thus, they are more likely to become alcoholic. Another study found that a specific genetic variation in D2 dopamine receptors (part of the brain’s reward system) will magnify the pleasurable impact of addictive substances and behaviors.[ii] Unsurprisingly, individuals with this genetic variation are more susceptible to addictions of all types.

Interestingly, genetic differences can also reduce the risk of becoming addicted. For example, people of East Asian ancestry are considerably less likely than other ethnic groups to be alcoholic. This is because they typically have a genetic variation that creates a deficiency of aldehyde dehydrogenase, an enzyme that is critical to the metabolism of alcohol. When individuals with this genetic variance (i.e., most East Asians) consume alcohol, they almost immediately experience unpleasant side effects, including headache, dehydration, nausea, sweating, and the like. Basically, consuming alcohol creates an instant hangover. For obvious reasons, alcoholism is rare among individuals with this genetic makeup.

Addiction can also be impacted indirectly by genetics.[iii] For example, we know that genetics are a factor with depression, anxiety, ADHD, bipolar disorder, and numerous other psychiatric symptoms and disorders. We also know that many people who face these issues choose to self-medicate (numb) with addictive substance and behaviors. This, of course, can lead to addiction. But this increased risk for addiction is unrelated to the ways in which addictive substances are processed in the brain and body. Similarly, heritable personality traits like impulsivity, reactivity, and risk-taking can indirectly increase the risk for addiction.[iv]

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If you or someone you know is struggling with an addiction—either substance or behavioral—plenty of help is available. To get started, check out the free resources on this website, or visit the Seeking Integrity website for information about professional treatment.


[i] Schuckit, M. A., & Smith, T. L. (1996). An 8-year follow-up of 450 sons of alcoholic and control subjects. Archives of General Psychiatry, 53(3), 202-210.

[ii] Comings, D. E., Muhleman, D., Ahn, C., Gysin, R., & Flanagan, S. D. (1994). The dopamine D2 receptor gene: a genetic risk factor in substance abuse. Drug and alcohol dependence, 34(3), 175-180, and, Comings, D. E., Ferry, L., Bradshaw-Robinson, S., Burchette, R., Chiu, C., & Muhleman, D. (1996). The dopamine D2 receptor (DRD2) gene: a genetic risk factor in smoking. Pharmacogenetics and Genomics, 6(1), 73-79, among other studies.

[iii] Goldman, D., Oroszi, G., & Ducci, F. (2005). The genetics of addictions: uncovering the genes. Nature Reviews Genetics, 6(7), 521-532, and, Kreek, M. J., Nielsen, D. A., Butelman, E. R., & LaForge, K. S. (2005). Genetic influences on impulsivity, risk taking, stress responsivity and vulnerability to drug abuse and addiction. Nature neuroscience, 8(11), 1450-1457, among other studies.

[iv] Goldman, D., Oroszi, G., & Ducci, F. (2005). The genetics of addictions: uncovering the genes. Nature Reviews Genetics, 6(7), 521-532.