Objective: To evaluate the effect of a preexisting posttraumatic stress disorder (PTSD) diagnosis on suicide and non-suicide mortalities among men with newly diagnosed prostate cancer, and examine potential mediating factors for the relationship between PTSD and suicide.

Methods: We used patient-level data from Veterans Health Administration electronic medical records to identify men (age ≥40 years) diagnosed with prostate cancer between 2004 and 2014. We used Fine and Gray regression model to estimate the risk for competing mortality outcomes (suicide, non-suicide, and alive). We used structural equation models to evaluate the mediating factors.

Results: Our cohort comprised 214,649 men with prostate cancer, of whom 12,208 (5.7%) had a preexisting PTSD diagnosis. Patients with PTSD compared to those without utilized more healthcare services and had lower risk cancer at diagnosis. Additionally, they experienced more suicide deaths (N = 26, 0.21% vs. N = 269, 0.13%) and fewer non-suicide deaths (N = 1399, 11.5% vs. N = 45,625, 22.5%). On multivariable analysis, PTSD was an independent suicide risk factor (HR = 2.35; 95% CI: 1.16, 4.78). Depression, substance use disorder, and any definitive prostate cancer treatment were partial mediators. However, PTSD was associated with lower non-suicide mortality risk (HR = 0.86; 95% CI: 0.77, 0.96).

Conclusion: Patients with PTSD experienced greater suicide risk even after adjusting for important mediators. They may have experienced lower non-suicide mortality risk due to favorable physical health resulting from greater healthcare service use and early diagnosis of lower risk cancer. Our findings highlight the importance of considering psychiatric illnesses when treating patients with prostate cancer and the need for interventions to ameliorate suicide risk.