Studies show that people with severe mental illness (SMI) have a greater risk of dying from colorectal cancer (CRC). These studies mostly predate the introduction of national bowel cancer screening programmes (NBCSPs) and it is unknown if these have reduced disparity in CRC-related mortality for people with SMI.

We compared mortality rates following CRC diagnosis at colonoscopy between a nationally representative sample of people with and without SMI who participated in Australia’s NBCSP. Participation was defined as the return of a valid immunochemical faecal occult blood test (iFOBT). We also compared mortality rates between people with SMI who did and did not participate in the NBCSP. SMI was defined as receiving two or more Pharmaceutical Benefits Scheme prescriptions for second-generation antipsychotics or lithium.

Amongst NBCSP participants, the incidence of CRC in the SMI cohort was lower than in the controls (hazard ratio [HR] 0.77, 95% confidence interval [CI] 0.61–0.98). In spite of this, their all-cause mortality rate was 1.84 times higher (95% CI 1.12–3.03), although there was only weak evidence of a difference in CRC-specific mortality (HR 1.82; 95% CI 0.93–3.57). People with SMI who participated in the NBCSP had better all-cause survival than those who were invited to participate but did not return a valid iFOBT (HR 0.67, 95% CI 0.50–0.88). The benefit of participation was strongest for males with SMI and included improved all-cause and CRC-specific survival.

Participation in the NBCSP may be associated with improved survival following a CRC diagnosis for people with SMI, especially males, although they still experienced greater mortality than the general population. Approaches to improving CRC outcomes in people with SMI should include targeted screening, and increased awareness about the benefits or participation.

Australian and New Zealand Clinical Trials Registry (Trial ID: ACTRN12620000781943).

People with severe mental illness (SMI) have a greater risk of dying from colorectal cancer (CRC), even though the incidence is lower or similar to that of the general population This pattern is unlikely to be solely explained by lifestyle factors, while the role of differences in cancer healthcare access or treatment is uncertain

We undertook a systematic review and meta-analysis on access to guideline-appropriate care following CRC diagnosis in people with SMI including the receipt of surgery, chemo- or radiotherapy. We searched for full-text articles indexed by PubMed, EMBASE, PsychInfo and CINAHL that compared CRC treatment in those with and without pre-existing SMI (schizophrenia, schizoaffective, bipolar and major affective disorders). Designs included cohort or population-based case–control designs.

There were ten studies (sample size = 3501–591 561). People with SMI had a reduced likelihood of surgery (RR = 0.90, 95% CI 0.92–0.97; p = 0.005; k = 4). Meta-analyses were not possible for the other outcomes but in results from individual studies, people with SMI were less likely to receive radiotherapy, chemotherapy or sphincter-sparing procedures. The disparity in care was greatest for those who had been psychiatric inpatients.

People with SMI, including both psychotic and affective disorders, receive less CRC care than the general population. This might contribute to higher case-fatality rates for an illness where the incidence is no higher than that of the general population. The reasons for this require further investigation, as does the extent to which differences in treatment access or quality contribute to excess CRC mortality in people with SMI.