Greater Risk of Breast Cancer in Women With Schizophrenia Interview with:
Chuanjun Zhuo, MD, PhD

Department of Psychiatric Laboratory
Department of Psychiatric Neuroimaging Faculty
Tianjin Mental Health Center
Tianjin, China What is the background for this study? What are the main findings? 

Response: According to previous epidemiological studies, women with schizophrenia may be associated with significantly increased risk of breast cancer. However, the results of these studies were not always consistent. In view of the fact that medical care for patients with schizophrenia is becoming multidisciplinary, we aimed to evaluate the risk of breast cancer in women with schizophrenia via a meta-analysis of relevant cohort studies. We included twelve cohorts and adopted the recently proposed prediction interval to evaluate the heterogeneity among the included studies.

We found that schizophrenia was associated with about 30% increased risk of breast cancer incidence in women. However, significant heterogeneity existed of the included studies, which indicates that more extensive researches into the potential mechanisms underlying the associations between schizophrenia and breast cancer risk are needed. What should readers take away from your report?

Response: Current pooled results support that women with schizophrenia are associated with significantly increased risk of breast cancer. However, differences in the characteristics of the previous cohort studies may affect the association and contribute to the heterogeneity of the meta-analysis. What are the clinical implications of your study?

Response: The results of this study have several important clinical implications.

  • First, results of our study are contrary to the previous hypothesis that schizophrenia may be protective against cancer. These results, together with our recent meta-analysis results showing no effect on lung cancer risk but a reduced hepatic cancer risk in schizophrenia, indicated that the association between schizophrenia and cancer risk may be complicated and depend on the cancer site.
  • Second, our results highlight that women with schizophrenia deserve intensive care for breast cancer screening and treatment. These gaps were also reflected by the results of our recent study showing that patients with schizophrenia are at a significantly increased risk of cancer mortality compared with the general population or individuals without schizophrenia, although the incidence of cancer in these patients may not be necessarily changed from the general population. To early prevent of breast cancer, an initial evaluation is needed to stratification the risk of breast cancer in women with schizophrenia.
  • Subsequently, antipsychotics that may increase prolactin level and expose higher breast cancer risk should be avoided in high-risk women.
  • Moreover, regular screening, including imaging or biomarker tests, should be performed. Besides, every effort should be made to improve the patients’ compliance during the prevention, treatment, and follow-up. What recommendations do you have for future research as a result of this work? 

Response: The most important task of future study, from our point of view, is to explore the potential mechanisms underlying the association between schizophrenia and breast cancer risk. These studies may be the key pathway to finally uncover the association between schizophrenia and breast cancer risk. In the context of significant heterogeneity among the previous published cohort studies on this topic, whether an updated meta-analysis is adequate to answer the question is of concern. Instead, big data based researches, such as the deep neural network analysis regarding the genetic or other biological association between schizophrenia and breast cancer risk may be optimal. Obviously, these studies are warranted. Is there anything else you would like to add? 

Response: Another important content is the current knowledge of the potential mechanisms underlying the association between schizophrenia and cancer. First, many clinical conditions that are commonly seen in patients with schizophrenia may also be risk factors for the development of breast cancer, such as obesity, lack of parity, and breast feeding. Moreover, as a hormone-dependent cancer, a significant positive association between plasma prolactin levels and the risk of breast cancer has been observed; in addition, increased prolactin levels have been observed in women with schizophrenia, particularly for those taking certain antipsychotics. Interestingly, it has also been indicated by James Michael Howard that low dehydroepiandrosterone and high testosterone in women with schizophrenia may be the underlying mechanisms of the connection between schizophrenia and risk of breast cancer. Finally, schizophrenia and breast cancer may share some other pathophysiological factors during their pathogenesis, including pathways involved in angiogenesis and cell cycle regulation. However, further experimental studies are needed to determine the exact mechanisms underlying the association between schizophrenia and breast cancer incidence.

As the lead author on the study I have no disclosures.


Zhuo C, Triplett PT. Association of Schizophrenia With the Risk of Breast Cancer IncidenceA Meta-analysis. JAMA Psychiatry. Published online March 07, 2018. doi:10.1001/jamapsychiatry.2017.4748 



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