Genetic Overlap of Schizophrenia and Bipolar Disorder

Kraepelin originally distinguished between dementia praecox and manic-depressive insanity, although he later admitted that he could not always tell the two disorders apart. Using MRI, these researchers examined specific white- and gray-matter abnormalities in 25 patients with schizophrenia, 37 patients with psychotic bipolar illness, and their unaffected first-degree relatives (36 and 50 relatives, respectively). All probands had at least one first- or second-degree relative with a nonorganic psychosis.

Using a model of genetic risk that they had constructed for each illness, the authors found that genetic risk for schizophrenia was associated with reduced gray-matter volume in the orbital, prefrontal, and premotor regions of the frontal cor…