Genetic risk refers to how inherited differences in DNA influence the chance of developing diseases such as heart disease, cancer or diabetes. Research shows that most common diseases are not caused by a single gene mutation, but by the combined effect of many genetic variants, each contributing a small amount to risk.

Scientists have developed polygenic risk scores to quantify this combined effect. These scores are calculated from hundreds to millions of genetic markers across the genome. People with high polygenic scores for a disease can have several times higher risk than the average person, sometimes approaching the risk seen in rare single gene disorders.

Large genome wide association studies in hundreds of thousands of individuals underlie these scores. They have identified many risk variants for conditions like coronary artery disease, breast cancer, type 2 diabetes and psychiatric disorders. Research shows that polygenic risk can help identify high risk individuals at younger ages, before symptoms appear, potentially guiding earlier screening or preventive measures.

However, the predictive power of polygenic scores varies by disease and ancestry. Scores developed in European populations often perform worse in other groups because of differences in genetic architecture and limited diversity in reference datasets. Environmental and lifestyle factors also interact with genetic risk, so a high genetic risk does not mean a disease is inevitable, and a low score does not guarantee protection.

Current research focuses on improving accuracy, expanding studies to diverse populations, integrating genetic and non genetic information and evaluating how to use genetic risk in clinical practice in a responsible and equitable way.