Genome-wide association studies (GWAS) help scientists identify genes associated with a particular disease (or another trait). This method studies the entire set of DNA (the genome) of a large group of people, searching for small variations, called single nucleotide polymorphisms or SNPs (pronounced “snips”). Each study can look at hundreds or thousands of SNPs at the same time. Scientists can then identify SNPs that occur more frequently in people with a certain disease than in people without it. These SNPs are said to be associated with the disease, and they can help researchers pinpoint genes that are likely involved in disease development.  

Because genome-wide association studies examine SNPs across the genome, they represent a promising way to study complex, common diseases in which many genetic variations contribute to a person’s risk. This approach has identified SNPs associated with several complex conditions including diabetes, heart disease, Parkinson's disease, and Crohn's disease. SNPs have also been associated with a person’s response to certain drugs and susceptibility to certain environmental factors such as toxins. Researchers hope that future genome-wide association studies will identify additional SNPs associated with chronic diseases and drug effects.  

Through genome-wide association studies, individual SNPs are identified that account for only a small percentage of disease risk. Together,  large numbers of SNPs  across the genome can help determine the overall risk of developing a disease or responding to particular drugs. Researchers can use information learned from genome-wide association studies to predict more accurately which prevention and treatment strategies will work in which groups of people, an important step in precision medicine.