The Relationship between Lithium Concentration in Drinking Water and Suicide Mortality: A Systematic Review

Title: The relationship between lithium concentration in drinking water and suicide mortality rate: A systematic review. Background: Suicide is one of the leading causes of death worldwide and is influenced by multiple factors. Recently, several studies have shown that lithium in drinking water is useful for reducing the suicide mortality rate. However, it is still uncertain whether lithium intake from drinking water can achieve an anti-suicidal effect. We performed a systematic review to determine the relationship between lithium in drinking water and suicide mortality rate. Methods and Findings: We reviewed articles related to the lithium concentration in drinking water and suicide mortality rate in various geographical areas between 1990 and 2020. Of 17 articles in our systematic review, 13 reported that lithium in drinking water was significantly negatively associated with standardized mortality ratio (SMR), while 4 studies did not show any associations. On the other hand, others with meta-analysis indicated that there was a negative association between lithium concentration in drinking water and suicide mortality rate. Conclusion: Most of the studies in this review revealed that lithium concentration in drinking water was inversely related to the expected suicide mortality rate in these studies. We reviewed these articles and maintain that the balance of lithium concentration in drinking water and SMR is important in determining whether lithium in drinking water affects suicide mortality rate. If the lithium concentration is stable over the entire study region, or suicide mortality rate is very low, an association between the lithium concentration in drinking water and suicide mortality rate could not be detected even with high lithium concentrations. Therefore, it may be difficult to evaluate the effect of lithium in drinking water on suicide. Further studies are needed to determine the factors related to suicide and lithium intake from sources other than drinking water to assess the relationship between tap water lithium concentration and suicide mortality rate.