The association between schizophrenia and cancer: a population-based mortality study

Background: For most of this century there has been speculation that persons diagnosed with schizophrenia have a reduced incidence of cancer. Objective: To determine if a history of cancer was more common in persons diagnosed with schizophrenia when compared with the general population, controlling for known risk and demographic factors. Design: We used the 1986 National Mortality Followback Survey (NMFS) which sampled 1% of all deaths in the US from that year. Data were obtained from death certificates and records of hospitalizations in the last year of life. Additional health and demographic data were obtained through interviews with decedents' families and other informants. We compared persons diagnosed with schizophrenia ( n=130) to individuals without schizophrenia ( n=18,603) and used logistic regression to determine the odds ratio for the occurrence of cancer in persons diagnosed with schizophrenia. Adjustment for age at death was done to correct for the fact that persons diagnosed with schizophrenia die on average 10 years younger than the general population. Main Outcome Measure: A diagnosis of cancer on a hospital record or the death certificate. Results: The unadjusted odds ratio for cancer among individuals with schizophrenia was 0.62 (95% confidence interval (CI) 0.40–0.96). After controlling for age, race, gender, marital status, education, net worth, smoking, and hospitalization in the year before death, we determined that the odds ratio for the diagnosis of cancer in persons with schizophrenia was 0.59 (95% CI 0.38–0.93). Conclusion: In this population-based study, we demonstrated a reduced risk of cancer among persons diagnosed with schizophrenia.