Mental health experts are nearly unanimous in endorsing the disease model of addiction. Alcoholism (now alcohol use disorder) was declared a disease in 1956 by the American Medical Association, and drug addiction (now drug use disorder) was declared a disease in 1987. The AMA was later joined by the American Psychological Association and many other professional organizations in defining addiction as a disease.

Like other diseases, addiction has a strong genetic basis that’s often triggered in high-risk environments. Those with genetic vulnerability are likely to develop addiction in cultures where alcohol and other drugs are readily available and frequently used. Where alcohol and drugs are less available and rarely used, genetic risk may never develop into addiction.

Many other diseases behave similarly. Genetic vulnerability to type II diabetes, for example, places people at high risk for diabetes in cultures like the United States, where diets are high in processed sugar. Genetic risk is far less likely to advance to diabetes in cultures where sugar intake is low.

When both genetic vulnerability and environmental risk are necessary for a disease to develop, the disease model can be difficult to grasp. Why doesn’t everyone with genes for addiction develop a substance use disorder? Isn’t it traumatic environments that cause addiction? And what about personal choice and people’s character?

These and other questions about the causes of addiction follow from what people see with their own eyes. Unlike patients with other diseases, many of us with addiction engage in behaviors while drinking or using that are just as harmful to people around us as they are to ourselves, engendering legitimate anger and distress. This explains why half of Americans view........

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