Investigation of the association between lithium levels in drinking water and suicide mortality in Hungary.

BACKGROUND: In recent decades, a series of ecological studies from various countries have attempted to reveal whether there is an association between trace amounts of lithium in drinking water and suicide mortality. With some notable exceptions, results have indicated that there is an inverse association between these two variables. Since Hungary had extremely high rates of suicide with a persistent spatial pattern, we consider that our country is ideal to investigate this research question. METHODS: We carried out our research on Hungarian data at the level of districts (n = 197). The dependent variable was the age- and gender-standardized mortality ratio for suicide (sSMR). Our main explanatory variable was the tap water lithium level (Li) from public drinking water supply systems using their own water source (n = 1 325). Those data, which give full national coverage, were aggregated to the level of districts. Confounding factors were religiosity, alcohol consumption and income. Various regression models were used for statistical calculations. RESULTS: Findings from our most appropriate regression model - adjusted for relevant confounding variables and able to handle spatial autocorrelation and heteroscedasticity - suggest a significant (p < 0.05) and a trend-like (p < 0.1) negative association between Li and sSMR in the total population and among males, respectively. However, such an association was not found between these two variables among females. CONCLUSION: In line with the majority of findings from other countries, our results indicate that the intake of lithium with drinking water may have a gender-dependent suicide-protective effect.

[Results of investigations on the association between lithium levels in drinking water and suicidal behaviour in the population: a narrative review].

INTRODUCTION: The risk of suicide is determined by the interplay of several interrelated factors from which psychiatric (especially affective) disorders are the most powerful predictors. Lithium, a mood stabilizer (which is also used to augment the efficacy of antidepressant therapy) has a well-established antisuicidal effect. In the last decades several studies investigated whether there is an association between the amount of lithium in tap water and suicide risk in the population. METHODS: A PubMed search was conducted to identify papers investigated the association between lithium levels in drinking water and suicide risk of the population. A "forward citation search" was also performed using the Google Scholar. Relevant papers were also tried to identify by going through the reference lists of the studies found during the Pubmed search ("backward citation search"). RESULTS: We identified more than 10 original studies on this topic. The majority of results suggest that higher lithium levels in drinking water are associated with decreased risks of suicide. Although, results are surprisingly concordant methodological limitations may decrease the validity of the findings. CONCLUSIONS: Results indicate that lithium intake from tap water in doses far below those used in the clinical practice may have suicide-preventive effects. This raises the possibility that lithium supplementation of tap water may open a new avenue in suicide prevention. In Hungary, where there is a stable in time spatial inhomogeneity of the suicide rate it would be especially interesting to test whether regional differences in lithium content of tap water contribute to this phenomenon.