Cancer risk not increased in schizophrenia, bipolar disorder

By Mark Cowen, Senior medwireNews Reporter

Results from a large UK study suggest that people with severe mental illness (SMI) are not at increased risk for developing common cancers.

Analysis of primary care data from The Health Improvement Network (THIN) for the period 1990-2008 revealed no significant difference between patients with and without an SMI regarding the incidence of common cancers overall or specific cancers.

The findings, published in Schizophrenia Research, "do not support the suggestion that people with SMI should be offered enhanced or targeted cancer screening," say lead researcher David Osborn (University College London) and colleagues.

The researchers compared the incidence of colon, rectal, colorectal, breast, and lung cancer among 20,632 adult patients with an SMI and 116,152 without an SMI over a median follow-up period of 6 years.

Amongst those with an SMI, the most common diagnoses were schizophrenia, bipolar disorder, and psychosis not otherwise specified.

In total, 380 patients with an SMI and 2736 without an SMI developed cancer during follow up.

After accounting for age, gender, period, social deprivation, and smoking, the team found that the overall risk for common cancers was not significantly increased among patients with an SMI compared with those without, at an adjusted incidence rate ratio (IRR) of 0.95.

Nor was the risk for individual cancers significantly increased among patients with an SMI compared with those without, at adjusted IRRs of 0.70, 1.05, 0.83, 1.23, and 0.84 for colon, rectal, colorectal, breast, and lung cancer, respectively.

The pattern did not differ significantly when the three main SMI diagnostic groups (schizophrenia, bipolar disorder, and other psychoses) were analyzed separately.

Osborn and team summarize: "In a cohort analysis within a large UK primary care database, the incidence of colo-rectal, breast and lung cancer, and of all common cancers, did not differ significantly in people with SMI, including schizophrenia, compared with people without SMI."

Nevertheless, they add that "although rates of cancer were similar in our cohorts, people with SMI still require equitable access to screening services for physical health conditions, including cancer screening."

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