Neuroscience, AnsweredWhat is risk?

August 14, 2026

What is risk? #

We often describe the likelihood of getting a disease with the term “risk.”  That’s because even in conditions mostly driven by genes, some people may experience severe symptoms, some will have mind symptoms, and some may have no symptoms at all. Risk is a number that quantifies the chances that someone with a given set of genetic or environmental conditions will develop symptoms.

Twin studies #

To understand how different factors contribute to risk of developing a condition, scientists design studies to control as many of these variables as possible. One powerful approach is a twin study.¹ In twin studies, researchers compare identical twins, who share 100% of their genes, with fraternal (non-identical) twins, who share about 50% of their genes, similar to other siblings. Because twins grow during the same pregnancy and are often raised in the same household, many environmental influences are similar between them. By comparing how often both twins in a pair develop the same condition, researchers can estimate how strongly genetics contributes to risk, relative to environmental factors.

Genome-wide association studies #

Another type of study often used to explore genetic risk is the “genome-wide association study”, or GWAS.^1,2 These studies recruit thousands (or hundreds of thousands) of participants, and look for which genetic variants are more likely to be found in people with a given condition. These studies tend to find a large number of genetic variants (sometimes hundreds), each of which contributes only a small amount of risk. Additional research is usually required to confirm and explore the role of each variant.