Lithium and Mental Health

According to Anna Fels, evidence is accumulating that the tiny amounts of lithium that occur naturally in the drinking water of some areas are good for mental health:

Researchers began to ask whether low levels of lithium might correlate with poor behavioral outcomes in humans. In 1990, a study was published looking at 27 Texas counties with a variety of lithium levels in their water. The authors discovered that people whose water had the least amount of lithium had significantly greater levels of suicide, homicide and rape than the people whose water had the higher levels of lithium. The group whose water had the highest lithium level had nearly 40 percent fewer suicides than that with the lowest lithium level.

Almost 20 years later, a Japanese study that looked at 18 municipalities with more than a million inhabitants over a five-year period confirmed the earlier study’s finding: Suicide rates were inversely correlated with the lithium content in the local water supply. More recently, there have been corroborating studies in Greece and Austria.

This strikes me as plausible. Our bodies need several metallic elements to survive; too little iron is associated with all sorts of problems. What if we do need lithium, in amounts greater that what we get naturally in some areas?