Breast cancer is a major global health issue, especially among women. Previous research has indicated a possible association between psychiatric conditions, particularly schizophrenia, and an increased risk of breast cancer. However, the specific risk of breast cancer in women with schizophrenia, compared with those with other psychiatric disorders and the general population, remains controversial and needs further clarification.

To estimate the risk of breast cancer among people with schizophrenia compared with people with other psychiatric disorders and people in the general population.

We utilised medical claims data of women aged 18 to 80 years in the Korean National Health Information Database from 2007 to 2018. Individuals with schizophrenia were defined as women with ICD-10 codes F20 or F25 (n = 224 612). The control groups were defined as women with other psychiatric disorders (n = 224 612) and women in the general Korean population (n = 449 224). Cases and controls were matched by index date and age, in a 1:1:2 ratio. We estimated the hazard of breast cancer using the Cox proportional hazards model, adjusting for insurance premiums and medical comorbidities. Among the people with schizophrenia, we used the landmark method to estimate the association between duration of antipsychotic medication use and the incidence of breast cancer.

In multivariable Cox regression models, the hazard rate of breast cancer was 1.26 times higher in the people with schizophrenia than in the general population (95% CI: 1.20–1.32). In comparison with the psychiatric patient group, the hazard ratio was 1.17 (95% CI: 1.11–1.28). Among women with schizophrenia, the hazard of breast cancer was greater among those who took antipsychotic medications for 1 year or more compared with those who took antipsychotics for less than 6 months.

Women with schizophrenia have an elevated risk of breast cancer, and long-term use of antipsychotics is associated with an increased risk of breast cancer.

乳腺癌是一个主要的全球健康问题，尤其是在女性中。先前的研究表明，精神疾病，尤其是精神分裂症，与乳腺癌风险增加之间可能存在关联。然而，与其他精神疾病患者和普通人群相比，精神分裂症女性患乳腺癌的具体风险仍然存在争议，需要进一步澄清。

评估精神分裂症患者与其他精神疾病患者和普通人群相比患乳腺癌的风险。

我们利用了 2007 年至 2018 年韩国国家健康信息数据库中 18 至 80 岁女性的医疗索赔数据。精神分裂症个体被定义为 ICD-10 代码为 F20 或 F25 的女性 （n = 224 612）。对照组被定义为患有其他精神疾病的女性 （n = 224 612） 和韩国普通人群中的女性 （n = 449 224）。病例和对照按索引日期和年龄以 1：1：2 的比例匹配。我们使用 Cox 比例风险模型估计乳腺癌的风险，并根据保险费和医学合并症进行调整。在精神分裂症患者中，我们使用具有里程碑意义的方法来估计抗精神病药物使用持续时间与乳腺癌发病率之间的关联。

在多变量 Cox 回归模型中，精神分裂症患者患乳腺癌的几率是普通人群的 1.26 倍 （95% CI： 1.20–1.32）。与精神病患者组相比，风险比为 1.17 （95% CI： 1.11-1.28）。在精神分裂症女性中，与服用抗精神病药物少于 6 个月的患者相比，服用抗精神病药物 1 年或以上的患者患乳腺癌的风险更大。

患有精神分裂症的女性患乳腺癌的风险较高，长期使用抗精神病药物与患乳腺癌的风险增加有关。