On Nature and Nurture

I collected these leaves on a dog walk. Many factors contribute to creating this amazing rainbow, including a plant's genetic code, ambient sunlight, nutrients, moisture, and temperature. For each of these variables, the timing, dose, and duration all play a role. Small shifts in one of these variables will change the ultimate expression of the color of the leaf.

Human development works the same way. Our genetic “blueprint” interacts continuously with our environment. Nature and nurture are partners in an elegant, ongoing dance of influence.

Research on the science of substance use disorders shows this interplay clearly. There are hundreds of genes that affect addiction, contributing to a 50% heritability if a parent has a substance use disorder. That’s a considerable number. However, 50% don’t inherit this condition, and that is where the environment comes in—family connection, peer influences, early childhood experiences, and especially, the age of first use.

Starting to use substances early strongly increases risk. Youth who drink regularly before age 15 have a fourfold higher likelihood of developing alcohol use disorder compared with those who delay until their twenties. Each year of delayed onset further reduces the risk.

For other inherited conditions, we routinely provide messages throughout childhood via parent advice and anticipatory guidance. If melanoma runs in the family, we teach kids to use sunscreen. If there’s high cholesterol, we model and emphasize the importance of nutrition and exercise. If color blindness or breast cancer is a concern, we might explain the limitations or discuss early screenings, respectively.

If substance use runs in the family, parents can communicate that genes may increase sensitivity, and that waiting to drink or experiment gives their brain time to mature. Not to cause alarm or anxiety. To communicate information and provide an expectation, as we do for many other hereditary conditions.