The Impact of Pre‐Existing Psychiatric Disorders on Gastric Cancer Stage and Mortality in Older Adults

Purpose The association between pre‐existing psychiatric disorders (PD) and gastric cancer outcomes has not been thoroughly investigated. This study evaluated whether PD, particularly serious pre‐existing psychiatric disorders (SPD), is associated with differences in gastric cancer stage at diagnosis, overall mortality, and cancer‐specific mortality. Methods We conducted a retrospective cohort study using SEER‐Medicare data (2000–2017) to identify patients aged ≥ 68 years diagnosed with gastric cancer. PD was defined as a Medicare claim for depressive disorder, anxiety disorder, adjustment disorder, psychotic disorder, bipolar disorder, or schizophrenia occurring 6–36 months before cancer diagnosis. SPD included claims for psychotic disorder, bipolar disorder, schizophrenia, or major depressive disorder (MDD). Multinomial logistic regression was used to assess stage at diagnosis. Cox proportional hazards and Fine‐Gray subdistribution hazard models were used to assess overall and cancer‐specific mortality, respectively. Results Among 15,882 patients, 1883 (12%) had PD. Patients with PD differed significantly from those with no pre‐existing psychiatric disorders (NPD) in terms of demographics, comorbidities, and cancer characteristics. Compared with NPD patients, those with PD were more likely to be diagnosed with early (in situ/local) stage cancer yet had higher overall mortality (aHR: 1.17, 95% CI [1.11, 1.23]) and cancer‐specific mortality (aSHR: 1.13, 95% CI [1.07, 1.21]). Patients with SPD also had higher risks of overall (aHR: 1.33, 95% CI [1.22, 1.45]) and cancer‐specific mortality (aSHR: 1.25, 95% CI [1.14, 1.38]). Conclusion Our findings highlight critical differences in gastric cancer outcomes among patients with PD and SPD. Despite being more likely to be diagnosed with early‐stage cancer, these patients experienced worse survival.