Lithium in Public Drinking Water and Suicide Mortality in Portugal: Initial Approach

Abstract

Introduction: Lithium can be found naturally in drinking water. There is some evidence that natural levels of lithium in drinking water may have a protective effect on suicide mortality. The aim of this study is to evaluate if higher natural concentrations of lithium in public drinking water are associated with lower local rates of suicide in Portugal.Material and Methods: Suicide standardized mortality ratios at 54 Portuguese municipalities within the 6-year period from 2011 to 2016 was correlated with lithium concentrations in public drinking water and socioeconomic factors using Pearson’s correlation coefficients (r) with one-tailed tests. Multivariate regression models were adjusted for well-known socioeconomic factors known to influence suicide mortality in Portugal (population density, average income per capita, unemployment rates and proportion of Roman Catholics).Results: The average lithium level, as evidenced by raw values for 54 municipalities, was 10.88 μg/L (standard deviation = 27.18). There was no statistically significant correlation between lithium levels and suicide standardized mortality ratio (r = 0.001, p-value = 0.996). There was a statistically significant higher suicide standardized mortality ratio for males (p-value = 0.000). When analyzed separately for both sexes, no statistically significant correlation between suicide standardized mortality ratio and lithium levels was found (male r = 0.024, p-value = 0.862; female r = 0.000, p-value = 0.999). No association between suicide standardized mortality ratio and socioeconomic factors was found: population density (r = -0.144, p-value = 0.300), average income per capita (r = -0.112, p-value = 0.418), unemployment rates (r = -0.001, p-value = 0.994), and proportion of Roman Catholics (r =- 0.150, p-value = 0.278).Discussion: Unlike most international studies regarding natural lithium levels and suicide risk, no inverse relation was found in Portugal. Factors such as the country’s low suicide rate, confunding suicide risk variables, and unaccounted lithium intake might have influenced these findings.Conclusions: No association between lithium in public drinking water and suicide rates was found in Portugal.

Association between lithium in tap water and suicide mortality rates in Miyazaki Prefecture

“…In this study, the mean and range of lithium levels in the tap water samples (mean, 2.8 μg/L; range, 0.2-12.3 μg/L) were lower than those found in other studies (range, 0.7-59 μg/) [9], (mean, 4.2 μg/L; range, 0-130 μg/L) [15]. Further, compared to previous studies that indicated no association between lithium levels in tap water and suicide mortality rates, a study in England [16] found a lower range (< 1-21 μg/L) similar to our study; however, another study conducted in Portugal found higher mean and range of lithium levels (mean, 10.88 μg/L; range, < 1-191 μg/L) [17]. In that study, the researchers considered that they found no correlation between lithium levels and suicide mortality rates because the suicide mortality rates of Portugal were lower than those in other studies, the unemployment rate was high, and the mean income was low.…”

“…Therefore, we evaluated the relationship between the range of lithium levels and crude suicide rates, separating them according to studies with an association (research that showed a significant association between lithium levels in tap water and suicide; if lithium levels increased, suicide rates decreased) and studies without such an association (research that did not show a significant association between lithium levels in tap water and suicide). We used lithium levels that were used in previous studies [9,10,[13][14][15][16][17]31] as well as crude suicide rates (per 100,000 population) from statistics on suicide provided by the Ministry of Health, Labor and Welfare in Japan and WHO [32]. Figure 3 shows the range of lithium levels in drinking water and crude suicide rates from eight previous studies and that of our study.…”

“…Areas A, B, C, and D are divided by dotted lines (the horizontal line shows crude suicide rates 25.8/100,000, and the vertical line shows the range of lithium levels 35.05 μg /L). We used lithium levels from previous studies [9,10,[13][14][15][16][17]31], as well as crude suicide rates (per 100,000 population) from statistics on suicide provided by the Ministry of Health, Labor and Welfare in Japan and WHO [32]. If crude suicide rates of the survey year were not available, we substituted crude suicide rates of the nearest survey year of lithium levels were 25.8/100,000 and 35.05 μg/L, respectively.…”

“…Recently, Ishii et al extended their investigation from one prefecture to Kyushu Island (a total of eight prefectures) and found that lithium levels in drinking water were negatively associated with male suicide mortality rates, after adjustment for potential confounding factors [15]. However, two studies, one in England and one in Portugal, indicated no association between lithium levels in drinking water and suicide mortality rates [16,17]. Knudsen et al performed a study using individual-level, register-based data for the entire adult Danish population (3.7 million individuals) from 1991 to 2012, linked with a moving 5year time-weighted average (TWA) with adjusted spatial autocorrelation (i.e., neighboring observations tend to be more alike compared to those further apart).…”

The association between lithium in drinking water and neuropsychiatric outcomes: A systematic review and meta-analysis from across 2678 regions containing 113 million people

“…After the full-text review, 10 papers were excluded. In total, 27 articles were included in our systematic review (Ando et al, 2017; Blüml et al, 2013; Dawson et al, 1970, 1972; Giotakos et al, 2013; Ishii et al, 2015; Kabacs et al, 2011; Kapusta et al, 2011; Kessing et al, 2017a, 2017b; Knudsen et al, 2017; Liaugaudaite et al, 2017, 2019; Ohgami et al, 2009; Oliveira et al, 2019; Oliver et al, 1976; Palmer et al, 2019; Parker et al, 2018; Pokorny et al, 1972; Pompili et al, 2015; Schrauzer and Shrestha, 1990; Schullehner et al, 2019; Shimodera et al, 2018; Shiotsuki et al, 2008, 2016; Sugawara et al, 2013; Voors, 1972), with 16 used in our meta-analysis (Blüml et al, 2013; Dawson et al, 1970; Giotakos et al, 2013; Ishii et al, 2015; Kabacs et al, 2011; Kapusta et al, 2011; Liaugaudaite et al, 2017, 2019; Ohgami et al, 2009; Oliveira et al, 2019; Palmer et al, 2019; Pompili et al, 2015; Schrauzer and Shrestha, 1990; Shiotsuki et al, 2016; Sugawara et al, 2013; Voors, 1972). A PRISMA flow diagram outlines this process (Figure 1), and a table of excluded studies after full-text review is provided as Supplementary Table 5.…”