Bottom Line: High groundwater concentration of lithium, a naturally occurring trace element, wasn't associated with any benefit in diagnoses of bipolar disorder or dementia when accounting for local health care resources and demographics, two factors that can cause mental health diagnosis rates to vary.
Why The Research Is Interesting: Previous research has suggested lithium may be associated with lower rates of mental health disorders. Mental health diagnosis rates can vary widely based on local health care resources and demographics, and this study accounted for those variables.
Who and When: Health care claims data for more than 4.2 million adults living in 174 U.S counties, among them more than 404,000 patients (9.6 percent) living in 1 of 32 counties with high lithium groundwater concentration of more than 40 μg/L.
What (Study Measures): County groundwater lithium concentrations, diagnoses identified from claims data, and county-level health care resources and demographics; frequency of bipolar disorder and dementia (outcomes); the analysis was repeated for three negative control outcomes (major depressive disorder, myocardial infarction and prostate cancer) that have no known link to groundwater lithium
How (Study Design): This was a population epidemiology study. A population epidemiology study describes characteristics of health and disease in one or more large populations, typically without detailed information about underlying causes.
Authors: William F. Parker, M.D., of the University of Chicago, and coauthors
Study Conclusions: Therapeutic doses of lithium are larger than groundwater lithium concentrations, making a true causal relationship between groundwater lithium and mental health "biologically dubious." 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.