Lithium in drinking water and suicide mortality.

BACKGROUND: There is some evidence that natural levels of lithium in drinking water may have a protective effect on suicide mortality. AIMS: To evaluate the association between local lithium levels in drinking water and suicide mortality at district level in Austria. METHOD: A nationwide sample of 6460 lithium measurements was examined for association with suicide rates per 100,000 population and suicide standardised mortality ratios across all 99 Austrian districts. Multivariate regression models were adjusted for well-known socioeconomic factors known to influence suicide mortality in Austria (population density, per capita income, proportion of Roman Catholics, as well as the availability of mental health service providers). Sensitivity analyses and weighted least squares regression were used to challenge the robustness of the results. RESULTS: The overall suicide rate (R(2) = 0.15, ß = -0.39, t = -4.14, P = 0.000073) as well as the suicide mortality ratio (R(2) = 0.17, ß = -0.41, t = -4.38, P = 0.000030) were inversely associated with lithium levels in drinking water and remained significant after sensitivity analyses and adjustment for socioeconomic factors. CONCLUSIONS: In replicating and extending previous results, this study provides strong evidence that geographic regions with higher natural lithium concentrations in drinking water are associated with lower suicide mortality rates.