An international research group has identified a 15% overlap between inherited schizophrenia and bipolar-disorder attributable to common genetic variation. The Cross Disorders Group of the Psychiatric Genomics Consortium published the study online in Nature Genetics August 11.

The group used genomewide-genotype data from thousands of people and compared them with control subjects. Besides the relationship between schizophrenia and bipolar disorder, there was a 10% inheritability overlap between bipolar disorder and depression, a 9% overlap between schizophrenia and depression, and a 3% overlap between schizophrenia and autism. The common genetic variants with small effects revealed in this and related studies will eventually be supplemented by other research on other variations. Study co-leader Naomi Wray, Ph.D., of the University of Queensland in Australia, said in a statement accompanying the study:

“Shared variants with smaller effects, rare variants, mutations, duplications, deletions, and gene-environment interactions also contribute to these illnesses. Since our study only looked at common gene variants, the total genetic overlap between the disorders is likely higher.” 

The study was funded in part by the National Institute of Mental Health. Read more about the work of the Psychiatric Genomics Consortium in Psychiatric News.