A genome-wide association study (GWAS) is a very large genetic study that seeks to uncover some of the biological roots of ME/CFS. By probing small DNA differences between people, a GWAS can help to pinpoint the genetic causes of disease and guide drug development. This design has previously been helpful in identifying genes together with molecular and cellular pathways that contribute to disease risk. (Read more about the science of GWAS.)

To work well, the study needs to recruit around 25,000 people with an ME/CFS diagnosis whose DNA will be compared with that of an even larger number of non-ME/CFS matched controls. These will be people from a similar population who do not have ME/CFS drawn from the half-million-strong UK Biobank.