Precis Future Med.  2020 Mar;4(1):21-30. 10.23838/pfm.2019.00093.

Two-sample Mendelian randomization study for schizophrenia and breast cancer

  • 1Samsung Advanced Institute for Health Sciences & Technology (SAIHST), Sungkyunkwan University, Samsung Medical Center, Seoul, Korea
  • 2Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
  • 3Department of Psychiatry, Veterans Health Service Medical Center, Seoul, Korea
  • 4Institute of Health and Environment, Seoul National University, Seoul, Korea
  • 5Department of Health Sciences, Graduate School of Public Health, Seoul National University, Seoul, Korea
  • 6Department of Psychiatry, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea


The purpose of this study was to investigate whether the risk of schizophrenia is causally associated with the risk of breast cancer.
Bidirectional two-sample Mendelian randomization (TSMR) was performed using genome-wide association study summary data from a total of 311,266 individuals. The causal relationship was estimated using an inverse-variance weighted method (IVW). For sensitivity analysis, weighted median, Mendelian randomization (MR)-Egger regression, and Mendelian randomization Pleiotropy RESidual Sum and Outlier (MR-PRESSO) were used.
The study showed evidence of a causal association between schizophrenia and the risk of breast cancer. In the IVW analysis, the odds ratio for breast cancer per log odds increase in schizophrenia risk was 1.069 with a 95% confidence interval of 1.028 to 1.112 (P< 0.001). This liability was consistently observed using multiple sensitivity analyses (P< 0.05). By contrast, the TSMR analysis of an inverted direction revealed no significant impact of breast cancer on the risk of schizophrenia.
Our results suggested that schizophrenia and breast cancer may have shared biological backgrounds. Genetic factors associated with schizophrenia might be causally associated with the risk of breast cancer.


Breast neoplasms; Causality; Genetic background; Genome-wide association study; Schizophrenia
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