Some of the disease correlations found in the mapping exercise have been previously observed, but many are new. Though Rzhetsky cautions that the work is preliminary, the results give some support to theories that autoimmune disorders and bacterial or viral infections might put people at risk for autism and diabetes.

The strongest results concern neurological disorders. "We're the first to quantify the overlap between schizophrenia, bipolar, and autism," says Rzhetsky. (See the slide show for maps showing the overlap between these diseases, as well as a map of migraine.)

For many of the diseases the Columbia researchers examined, specific genetic risk factors are known. Researchers can examine the role of these genes in more poorly understood diseases that overlap with a better understood one.

Karp says that he hopes Rzhetsky's work will "lead to new avenues of research" and that other researchers will expand on it to include more patients, increasing its statistical power.