Tap water that contains lithium may cut the risk of suicide, according to a Japanese study that looked at people in the prefecture of Oita.
Areas in the prefecture with the highest levels of lithium in drinking water had much lower rates of suicide than other areas, said the researchers from the universities of Oita and Hiroshima, BBC news reported.
The findings, published in the British Journal of Psychiatry, warrant further research, but the study authors did not suggest that lithium should be added to drinking water.
Lithium is used to treat certain mood disorders, such as bipolar disorder.
"However, lithium also has significant and unpleasant side effects in higher doses and can be toxic," Sophie Corlett, external relations director at the mental health charity Mind in the U.K., told BBC News. "Any suggestion that it should be added, even in tiny amounts, to drinking water should be treated with caution and researched very thoroughly."