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What are genome-wide association studies?
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Genomicresearch

What are genome-wide association studies?

Genome-wide association studies scan thousands of SNPs across the genome to pinpoint genetic variants linked to diseases, drug responses, and environmental susceptibilities.

Overview

Genome-wide association studies (GWAS) help scientists identify genes associated with a particular disease or other 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.

Why GWAS are valuable

Because GWAS 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 GWAS will identify additional SNPs associated with chronic diseases and drug effects.

Risk assessment and precision medicine

Through GWAS, 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 GWAS to predict more accurately which prevention and treatment strategies will work in which groups of people, an important step in precision medicine.

Resources for further information

The National Human Genome Research Institute provides a detailed explanation of GWAS. In addition, the National Human Genome Research Institute and the European Bioinformatics Institute jointly provide a Catalog of Published Genome-Wide Association Studies.

ClinicalTrials.gov, a service of the National Institutes of Health, provides easy access to information about clinical trials and offers a list of GWAS that are accepting (or will accept) participants.

For more technical information, the NCBI’s Database of Genotypes and Phenotypes (dbGaP) contains data from GWAS.

Related topics

  • What are single nucleotide polymorphisms (SNPs)?
  • What are genome-wide association studies?
  • What is pharmacogenomics?
  • What are genome editing and CRISPR-Cas9?

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Frequently Asked Questions

single SNP usually confers only a modest increase in risk (often less than 2‑fold). Risk is cumulative; many SNPs together, along with lifestyle factors, determine overall risk. A positive result should be interpreted in the context of family history, environmental exposures, and other health factors.
Yes, pharmacogenomic GWAS have identified SNPs that affect drug metabolism (e.g., CYP2C19 variants influencing clopidogrel efficacy). Your clinician can use this information to adjust drug choice or dose, but it is usually one piece of a larger clinical decision.
You can request a direct‑to‑consumer genetic test that reports on known GWAS‑identified SNPs, or you can ask your clinician to order a panel that includes those variants. Many labs provide a summary of your risk profile based on your genotype.
Most GWAS have been conducted in populations of European ancestry, so the identified SNPs may not have the same effect sizes or frequencies in other groups. Researchers are increasingly conducting multi‑ethnic studies, but you should discuss with your clinician whether the findings are applicable to your background.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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