“Association Between Groundwater Lithium and the Diagnosis of Bipolar Disorder and Dementia in the United States”, 2018-07 (; backlinks; similar):
Groundwater lithium concentrations were collected by the US Geological Survey from more than 3000 drinking water wells 1992–11200321ya…Claims data for 4,227,556 adults living in 174 counties were analyzed, including 3,046,331 with private insurance, 261,461 with Medicare Supplemental, and 919,764 with Medicaid. Among them, 404,662 patients (9.6%) lived in 1⁄32 counties with high lithium (>40 μg/L). The mean and median lithium concentrations were 27.4 μg/L and 11.1 μg/L, respectively (IQR, 3.7–23.6 μg/L).
Unadjusted prevalence rates for all outcomes were statistically-significantly lower in high-lithium counties. However, high-lithium counties had fewer physicians and health care resources and had smaller, younger, less educated, and more Hispanic populations (Table).
After adjustment for county-level demographics and health care resources, high lithium did not confer any statistically-significant benefit for bipolar disorder, dementia, or the negative controls major depressive disorder, myocardial infarction, or prostate cancer. The Figure shows the lack of any association across the entire lithium distribution.
Discussion: Despite the substantial variation in groundwater lithium exposure in the United States, we found no statistically-significant association between groundwater lithium exposure and risk of bipolar disorder or dementia after adjustment for county-level demographics and health care resource. This indicates the purported association of high-lithium concentrations in drinking water with mental health disorders is driven by unaccounted variation in demographics, health care resources, and diagnosis practices.
Therapeutic lithium doses are orders of magnitude larger than groundwater lithium concentrations, making a true causal relationship between groundwater lithium and mental health biologically dubious. In our study, the high-lithium group was exposed to a mean of 141.3 μg/L in their water supply. This means that a patient would need to drink more than 1,000 L of water a day to ingest the lowest reported effective therapeutic lithium dose of 150 mg.