Summary:
This study was a systematic review and meta-analysis that examined whether naturally occurring lithium levels in public drinking water are associated with suicide rates in the general population. Suicide remains a major global public health issue, causing more than 800,000 deaths each year. Individuals with mental health conditions, particularly mood disorders such as depression and bipolar disorder, are at substantially higher risk. Lithium is a known treatment for bipolar disorder and is effective in stabilising mood, reducing depressive and manic episodes, and lowering suicide risk. Evidence also suggests lithium may reduce aggression and impulsivity. Lithium occurs naturally in the environment and is present in varying concentrations in rocks, soil, food, and drinking water. Previous research has reported lower rates of suicide in regions with higher naturally occurring lithium concentrations in water supplies, leading to the hypothesis that lithium exposure may have a protective effect. To investigate this relationship, this study identified 15 eligible studies to examine associations between lithium concentrations in drinking water and suicide mortality rates. The findings showed a consistent inverse association between lithium levels in drinking water and suicide mortality, meaning areas with higher lithium concentrations generally reported lower suicide rates. The authors concluded that the available evidence from the studies supports a potential protective association between naturally occurring lithium in drinking water and suicide mortality. However, because the types of studies included were ecological studies, they cannot be used to establish causation. The results do however suggest that further research, including randomised trials, may help determine whether lithium exposure could contribute to suicide prevention.
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Abstract:
Background: The prevalence of mental health conditions and national suicide rates are increasing in many countries. Lithium is widely and effectively used in pharmacological doses for the treatment and prevention of manic/depressive episodes, stabilising mood and reducing the risk of suicide. Since the 1990s, several ecological studies have tested the hypothesis that trace doses of naturally occurring lithium in drinking water may have a protective effect against suicide in the general population. Aims: To synthesise the global evidence on the association between lithium levels in drinking water and suicide mortality rates. Method: The MEDLINE, Embase, Web of Science and PsycINFO databases were searched to identify eligible ecological studies published between 1 January 1946 and 10 September 2018. Standardised regression coefficients for total (i.e. both genders combined), male and female suicide mortality rates were extracted and pooled using random-effects meta-analysis. The study was registered with PROSPERO (CRD42016041375). Results: The literature search identified 415 articles; of these, 15 ecological studies were included in the synthesis. The random-effects meta-analysis showed a consistent protective (or inverse) association between lithium levels/concentration in publicly available drinking water and total (pooled β = −0.27, 95% CI −0.47 to −0.08; P = 0.006, I2 = 83.3%), male (pooled β = −0.26, 95% CI −0.56 to 0.03; P = 0.08, I2 = 91.9%) and female (pooled β = −0.13, 95% CI −0.24 to −0.02; P = 0.03, I2 = 28.5%) suicide mortality rates. A similar protective association was observed in the six studies included in the narrative synthesis, and subgroup meta-analyses based on the higher/lower suicide mortality rates and lithium levels/concentration. Conclusions: This synthesis of ecological studies, which are subject to the ecological fallacy/bias, supports the hypothesis that there is a protective (or inverse) association between lithium intakes from public drinking water and suicide mortality at the population level. Naturally occurring lithium in drinking water may have the potential to reduce the risk of suicide and may possibly help in mood stabilisation, particularly in populations with relatively high suicide rates and geographical areas with a greater range of lithium concentration in the drinking water. All the available evidence suggests that randomised community trials of lithium supplementation of the water supply might be a means of testing the hypothesis, particularly in communities (or settings) with demonstrated high prevalence of mental health conditions, violent criminal behaviour, chronic substance misuse and risk of suicide.
Article Publication Date: 27/07/2020
DOI: 10.1192/bjp.2020.128
