Genetic risk refers to how inherited differences in DNA influence a person’s likelihood of developing disease. Research over the last two decades has transformed this idea from rare single gene disorders to a spectrum of risk shaped by thousands of common variants.

Early work focused on high impact mutations such as those in BRCA1 and BRCA2, which greatly increase the risk of breast and ovarian cancer. These mutations are rare but powerful: carrying one can shift lifetime risk from the population average to well above 50 percent. Similar high risk variants exist for conditions like familial hypercholesterolemia and some forms of colon cancer.

More recent studies use genome wide association approaches, scanning millions of genetic markers in large populations. Each common variant typically has a small effect, but when combined into a polygenic risk score they can explain a substantial portion of risk for diseases such as coronary artery disease, type 2 diabetes and common cancers. Individuals in the highest few percent of these scores can have a several fold increased risk compared with average.

Genetic risk is always probabilistic, not destiny. Environment and lifestyle including smoking, diet, physical activity and infections can amplify or reduce inherited risk. In some cases, healthy behaviors can bring the risk of a genetically predisposed person close to that of someone without such predisposition.

Current research focuses on improving the accuracy and diversity of risk scores, integrating genetic risk with clinical data and using this information for earlier screening, targeted prevention and more personalized treatment decisions.