Understanding Individual Vulnerability to Addiction

Consider two adult siblings who grew up in the same household and same family atmosphere. One sibling can drink socially—he enjoys a beer now and then, but overall, he can take it or leave it—while the other sibling completely loses control over his alcohol consumption and faces years of negative consequences due to his alcohol use.

Why does this happen? Some erroneously believe the distinction lies in the siblings’ character or morality. They may say, “Well the answer is clear. One sibling is responsible, intelligent, and a good person, while the other is weak, irresponsible, and selfish.” This sentiment is the heart of the “moral model of addiction”—the belief that substance use disorders result from moral failings or character flaws—that people choose to become addicted and they could stop using if they wanted to (and since they don’t, they must be selfish). All they have to do is “just say no.”

Despite decades of research indicating that addiction is a brain disease (Leshner, 2001), many people still fall into the alluring trap of the moral model. And it’s easy to do—people with addiction often do things that hurt others, thus the conclusion that they themselves must be “bad people” is easy to adopt.

But what do we actually know about a person’s susceptibility to addiction? What makes one person more vulnerable to the rewarding effects of alcohol and other drugs of abuse than another person?

The American Society of Addiction Medicine (ASAM; 2019) clearly tells us that addiction is:

1. A medical disease.
2. Effected by an individual’s brain circuitry.
3. Effected by an individual’s genetics.
4. Effected by an individual’s environment.
5. Effected by an individual’s life experiences.

Thus, rather than a simple moral model conclusion, the ASAM definition tells us that addiction is complex. It is the result of a person’s neurobiological functioning, heredity and genes, the situations in which they have lived, their childhood experiences, and their subsequent life circumstances. Some who hear this definition may immediately respond with the question, “So everyone with addiction is off the hook? No one is responsible?” And to that, clinicians and researchers would respond that understanding the cause and contributing factors of addiction does not absolve an individual of their behavior—but it does help us have an accurate understanding of the disease, which can aid in both prevention and treatment.

Decades of research reveal that some people have genetic vulnerabilities that may make them more susceptible to addiction. These genetic vulnerabilities are linked to the functioning of the individual’s reward circuitry in the brain (Blum et al., 1996; Blum et al., 2012; Grant et al., 2006; Gold et al., 2014; Leeman & Potenza, 2013) and can predispose an individual to the rewarding nature of drugs of abuse and/or addictive behaviors. Although genetics is only part of the equation (rather than the entire equation), it is an important component.

In addition to genetics, research indicates that addiction also is influenced by age of first use of a drug of abuse (younger drug initiation is linked with higher risk of adult substance use due to the period of brain development; Chen et al., 2010), adverse childhood experiences and trauma (which may lead to a dysregulated stress response system, to which drugs of abuse may become maladaptive coping strategies; Dube et al., 2003; Felitti et al., 1998; Nakazawa, 2015), and exposure to drug use and addictive behavior in one’s family, peer group, or community (social learning and modeling of behaviors; Akers & Lee, 1996).

Therefore, people vary in their susceptibility to addiction based on a wide variety of factors. Genes, brain circuitry, early life experiences, and social settings can all play a part. As we embrace this complex understanding of the etiology of addiction, we can move away from a moral model evaluation and step into a holistic, empathic understanding that will advance the field of addiction treatment.