A Japanese study suggests that drinking water containing the element lithium may decrease the risk of suicide.
In the British Journal of Psychiatry study, researchers examined levels of lithium in drinking water and suicide rates in the prefecture of Oita, which has a population of more than one million.
From analyses, scientists found that the suicide rate was significantly lower in those areas with the highest levels of the element.
But the team from the universities of Oita and Hiroshima found that even relatively low levels appeared to have a positive impact of suicide rates.
Levels ranged from 0.7 to 59 micrograms per litre, reports The BBC.
The researchers speculated that while these levels were low, there may be a cumulative protective effect on the brain from years of drinking this tap water.
The findings have led some researchers to call for further study to consider the public health benefits of adding lithium to drinking water supplies.