Medicine has traditionally grouped conditions based on anatomy, symptoms, or even cultural and historical associations.

A team from the University of Chicago proposes that patients and doctors alike would better benefit by looking for the devil right in the details: the genesis of disease within the DNA of the afflicted, as they propose in a new paper in the journal Nature Genetics.

“The large number of families in this study allowed us to obtain precise estimates of genetic and environmental correlations, representing the common causes of multiple different diseases,” said lead author, Kanix Wang. “Using this shared genetic and environmental causes, we created a new system to classify diseases based on their intrinsic biology.”

The study utilized insurance claims from a full third of the U.S. population, through a source called the Truven MarketScan. That massive trove was cut back to a subset of 128,989 families, encompassing 481,657 individuals, they report.

Among this group, they assessed the most common 149 diseases – but especially the 29 that appeared to have high heritability between children and parents. 

Some surprising connections were made that aren’t completely intuitive.

For instance, migraines are most genetically similar to irritable bowel syndrome. The environmental similarities instead link migraines to other inflammatory diseases: cystitis and urethritis.

Other connections included ADHD with non-melanoma skin cancer, adjustment disorder with general hypertension, and allergic rhinitis with type 1 diabetes, according to the study. 

But some other conclusions were more of an intuitive connection. Some neurological and psychiatric diseases – schizophrenia, bipolar disorder, substance, among them – have environmental triggers that are nearly as strong as the genetic causation component.

The new way of thinking about pathology could open new doors for treatment that haven’t even been considered yet, according to the researchers.

“Understanding genetic similarities between diseases may mean that drugs that are effective for one disease may be effective for another one,” said Andrey Rzhetsky, the paper’s senior author. “And for those disease with a large environmental component, that means we can perhaps prevent them by changing the environment.”