The risk of getting a psychiatric illness is largely heritable — and many of the genetic variants involved seem to be shared across disorders.

The international Cross-Disorder Group of the Psychiatric Genomics Consortium identified common genetic variants in more than 30,000 patients diagnosed with one of five psychiatric disorders, and compared these with thousands of non-diagnosed controls.

These variants accounted for 17–29% of risk for the illnesses, and there is substantial overlap between disorders. For example, in schizophrenia, 15% of the variants overlapped with bipolar disorder, 9% with depression and 3% with autism.

Nature Genet. http://dx.doi.org/10.1038/ng.2711 (2013)