A shared genetic contribution to breast cancer and schizophrenia

An association between schizophrenia and subsequent breast cancer has been suggested; however the risk of schizophrenia following a breast cancer is unknown. Moreover, the driving forces of the link are largely unclear. Here, we report the phenotypic and genetic positive associations of schizophrenia with breast cancer and vice versa, based on a Swedish population-based cohort and GWAS data from international consortia. We observe a genetic correlation of 0.14 (95% CI 0.09–0.19) and identify a shared locus at 19p13 ( GATAD2A ) associated with risks of breast cancer and schizophrenia. The epidemiological bidirectional association between breast cancer and schizophrenia may partly be explained by the genetic overlap between the two phenotypes and, hence, shared biological mechanisms. Schizophrenia has been associated with increased risk of breast cancer, yet the risk of schizophrenia following breast cancer is unclear. Here, the authors show a bidirectional association between breast cancer and schizophrenia in Sweden and a shared genetic contribution to both diseases.