Altered cancer mortality among psychiatric patients has been reported, but competing death causes were often ignored.

To investigate whether observed cancer mortality in patients with various psychiatric disorders might be biased by competing death causes.

To assess the importance of cancer as death cause and as cause of physical comorbidity among patients with a mental illness.

In this retrospective cohort study on data from the Psychiatric Case Register Middle Netherlands linked to the death register of Statistics Netherlands, the risk of cancer death among patients with schizophrenia (N = 4,590), bipolar disorder (N = 2,077) and depression (N = 15,130) and their matched controls (N = 87,405) was analyzed using a competing risk model.

Compared to controls from the general population, higher hazards of cancer death were found in patients (schizophrenia: HR = 1.61, 95%CI: 1.26−2.06; bipolar disorder: HR = 1.20, 95%CI: 0.81−1.79), depression: HR = 1.26, 95%CI: 1.10− 1.44). However, the HRs of death due to suicide and other death causes were more increased. Therefore, among those who died, the 12-years-cumulative risk of cancer death was significantly lower among the three patient groups.

Our analysis shows that, compared to the general population, patients with a mental illness are at higher risk of dying from cancer, given that they survive the much more increased risks of suicide and other death causes.