Cancer morbidity in psychiatric patients: Influence of lithium carbonate treatment

Background: The relationship between mental diseases and cancer development has been examined in a number of studies but the findings are still inconclusive and suffer from methodological problems. Studies conducted to examine the effect of lithium on malignant cells yielded inconsistent results. Objective: To assess cancer morbidity in patients with psychiatric disorders treated with lithium carbonate. Method: The study group included 609 patients treated by lithium carbonate and 2,396 controls not treated by lithium at the 3 index hospitals. The combined file of patients and controls was matched with the Nationwide Central Cancer Registry, by ID numbers and first names. The latter includes all malignant disorders diagnosed in Israel starting in 1960. End of follow-up was fixed at December 31, 1996. Results: A lower but non-significant risk (RR=0.79; CI=0.17-3.60) to develop nonepithelial tumors was found among lithium carbonate treated psychiatric patients as compared to controls. A significantly (P=0.05) inverse trend of cancer with lithium dose was observed. The risk of cancer development among each group of psychiatric patients was significantly lower than in the population (RR=0.68 for the lithium treated group versus 0.78 for controls). Conclusion: Mental patients have a lower cancer prevalence than the general population and lithium may have a protective effect.