Objective: Controversy concerning cancer incidence in schizophrenia exists because of heterogeneous study findings.
Method: A meta-analysis was performed on standardized incidence ratios (SIR) of cancer in patients with schizophrenia and first-degree relatives and compared with general population samples.
Results: The pooled overall cancer incidence in patients was not significantly increased (SIR = 1.05, CI 0.95-1.15). Lung cancer incidence was slightly increased (SIR = 1.31, CI 1.01-1.71), but was reduced after adjusting for smoking prevalence. The incidence of several cancers unrelated to smoking was reduced in patients. Breast cancer rates were significantly increased in female patients. The pooled overall cancer incidence in siblings (SIR = 0.89, CI 0.84-0.94) and parents (SIR = 0.90, CI 0.88-0.93) was significantly reduced. A meta-regression detected a significant relationship between cancer risk in the general population and relative risk in patients.
Conclusion: The meta-analysis aided exploration of inconsistent study findings. There is a discrepancy between cancer risk exposure and cancer incidence in schizophrenia consistent with a protective effect.