Drinking water which contains the element lithium may reduce the risk of suicide, a Japanese study suggests.

一项日本调查显示 ，喝含有锂元素的水可能降低自杀的风险。

The protective effect could be the result of years of drinking this water

Researchers examined levels of lithium in drinking water and suicide rates in the prefecture（任期，管区） of Oita, which has a population of more than one million.

The suicide rate was significantly lower in those areas with the highest levels of the element, they wrote in the British Journal of Psychiatry¹（精神病学）.

High doses of lithium are already used to treat serious mood disorders³.

But the team from the universities of Oita and Hiroshima found that even relatively⁴ low levels appeared to have a positive impact of suicide rates.

Levels ranged from 0.7 to 59 micrograms per litre. The researchers speculated（深思，推测） that while these levels were low, there may be a cumulative⁵（累积的） protective effect on the brain from years of drinking this tap water.

Added element

At least one previous study has suggested an association between lithium in tap water and suicide. That research on data collected from the 1980s also found a significantly lower rate of suicide in areas with relatively high lithium levels.

The Japanese researchers called for further research in other countries but they stopped short of any suggestion that lithium be added to drinking water.

The discussion around adding fluoride（氟化物） to water to protect dental health has proved controversial - criticised by some as mass involuntary（自然而然的，无意识的） medication.

In an accompanying editorial（社论）, Professor Allan Young of Vancouver's Institute for Mental Health said "this intriguing⁶（吸引人的，有趣的） data should provoke（激起，惹起） further research.

"Large-scale trials involving the addition of lithium to drinking water supplies may then be feasible, although this would undoubtedly⁷ be subject to considerable debate. Following up on these findings will not be straightforward⁸ or inexpensive, but the eventual⁹ benefits for community mental health may be considerable."

Sophie Corlett, external relations director at mental health charity Mind said the research "certainly merits（功绩） more investigation¹⁰.

"We already know that lithium can act as a powerful mood stabiliser for people with bipolar（双极的） disorder², and treating people with lithium is also associated with lower suicide rates.

"However, lithium also has significant and an unpleasant side effects in higher doses, and can be toxic¹¹（有毒的）. Any suggestion that it should be added, even in tiny amounts, to drinking water should be treated with caution and researched very thoroughly¹²."