Genetics: Polygenic Risk

Polygenic risk refers to the combined influence of many genetic variants, each usually contributing a small effect. Researchers can combine associations into a polygenic risk score. The score summarises selected genetic information relative to the population used to develop it; it is not a direct measurement of illness or a complete account of inherited susceptibility.

Genetics influences susceptibility to schizophrenia, but inheritance is complex. Many genetic differences can contribute, and their effects interact with development and environment. A genetic association describes probability across populations, not an inevitable outcome for one person. Most findings do not provide a simple explanation for an individual diagnosis.

Predictive performance varies with ancestry, study design and the outcome considered. A score may help research while remaining insufficient for routine individual diagnosis or treatment selection. Many people with higher scores will not develop schizophrenia, and illness can occur at lower scores. Environmental and developmental factors are not fully represented. Interpretation also raises privacy and fairness concerns. Public explanations should distinguish statistical association from clinical usefulness and avoid presenting commercial testing as a reliable forecast of one person’s psychiatric future.

A polygenic score is built from the variants and effect estimates available in a study. It leaves out influences that were not measured or captured accurately. Scores also need validation in the population where they are used. These limitations explain why an association valuable for research may provide insufficient accuracy or benefit for routine decisions about an individual’s psychiatric care.

Further reading: National Institute of Mental Health; Nature: schizophrenia genetics study.