Small amounts of natural lithium in drinking water lowers suicide rates, Austrian scientists said in a study presented by the Medical University of Vienna.
Lithium has been used for several decades for treating mental illness, including depression.
The team of medical researchers compared lithium levels in water with suicide rates in all 99 Austrian districts and found a significant correlation between the two factors.
The statistical relationship was significant even after taking into account factors such as income and availability of community health services, which are known to influence suicide numbers.
Japanese scientists had reached similar conclusions in 2009, but their work was criticised for methodical shortcomings, the Medical University said in a statement.
Nestor Kapusta, the lead scientist of the Austrian study, said he was surprised that these trace amounts of lithium have an effect.
"Dosage in therapy is around 100 times higher than the natural level in drinking water," he said.
But Kapusta warned against enriching water with lithium to prevent suicides. Broad studies and analyses of side effects were needed first, he said.
Lithium must not be seen as a cure-all in suicide prevention, the study authors stressed. Instead, they advocated a mix of measures such as improving health services, education of the public and gun control.
(Sapa, Albert Otti, June 2011)