Lithium is an element. It is the lightest solid and metal on the periodic table. It is primarily produced in South America but exists in large amounts in seawater and rock. It is considered a trace mineral and not typically labeled on food or water that we consume. It is also used in high doses to treat bipolar disorder. Various other industrial uses also exist.
Nutritionally speaking lithium helps your body metabolize cobalamin (Vitamin B12). Vitamin B12 is implicated in a lot of things and primarily comes from animal products. Vegans have to supplement B12 in order to get enough and many modern people across different diets continue to be deficient in it. Lithium helps us metabolize cobalamin to prevent deficiency.
Several studies have now discovered a fairly strong (statistically significant, but with some caveats around gender) correlation between the naturally occurring lithium level in water and the suicide, self harm and violent crime rate in a given area. For men in particular, the higher the natural lithium content in the water, the less they kill themselves. The difference between areas with high lithium content and low lithium content are significant and pronounced.
A recent study tried to reproduce whether this effect holds through other locales. The original and most often cited studies took place across Japan and Texas. Both of them found a strong correlation between suicide and lithium content in the water when they looked across regions. The recent study proved the correlation for natural lithium and disproved an idea that this could be caused by lithium prescriptions leaking into the water supply. The effect came from the natural lithium already in the water, and the correlation held.
During water processing, the only material we currently supplement it with is fluoride. Fluoride is controversial but has been shown to reduce cavities in a population when added to the water supply. It has some adverse effects but the trade offs are considered worth it by most medical advisory boards and government health agencies. Why do we not pursue a similar strategy for lithium? What implications would that have on public health and safety?
Lithium the drug contains 200-400x the amount a person would normally get from diet. It requires regular blood tests and monitoring from a health professional and lithium toxicity can become fatal and cause more problems than the drug helps. The occurrence of lithium toxicity is uncommon even from dosages that high. It appears from the studies that doses as small as 3x more than baseline can have statistically significant effects on reducing suicide.
The variance on natural lithium content in water is significant. It varies as much as 5x across locales. If high lithium content is bad, we should we filtering it out of water if it varies that much. Given how significant and positive an effect high lithium content has on suicide rates, we should really be adding lithium salts to our drinking water to bring it up to reduce suicide.
The benefit would be a significant reduction in self harm and suicide and a small reduction in violent crime. Lithium salt is inexpensive compared to many existing programs and treatment options for these issues. And we know it is safe since people have been drinking high lithium content water in certain areas of the world without issue. It is worth testing in a certain locale to see if it does have the positive effects hypothesized in the studies.