Key findings include that every person’s genome includes around five million variants, or locations in the DNA that differ between individuals. These include around 10,000 that alter gene sequences, which can have a positive or negative effect – ranging from lactose intolerance to drug response – but are often biologically neutral. Every person also has between one and three rare variants that have previously been shown to cause serious genetic diseases, and another 50 rare variants that are currently of uncertain clinical relevance.

The team also analysed numerous polygenic risk scores, which take into account all known genetic factors to calculate risk of getting a disease in future. Looking at polygenic scores for 28 common conditions – such as diabetes, cardiovascular disease and schizophrenia – they found that most people would be categorised as at high risk  of genetic risk for around three conditions. The team did not investigate the health status of any of the participants, so many of these participants might not have any diseases. The study underlines that such findings can be part of normal genetic variation, and other factors are crucial in development of disease.