Lithium in the water supply

There is an interesting proposal in the Irish Times

Psychiatrist calls for lithium to be added to water

A consultant psychiatrist last night called on Government to add lithium salts to the public water supply in a bid to lower the suicide rate and depression among the general population.

At a mental health forum on “Depression in Rural Ireland” in Ennistymon, Co Clare, Dr Moosajee Bhamjee said that “there is growing scientific evidence that adding trace amounts of the drug lithium to a water supply can lower rates of suicide and depression”.

I would like to see what this scientific evidence is. The studies I have seen are from Japan where the lithium is naturally occuring. And one from Texas that seems a bit dodgy

Drinking water which contains the element lithium may reduce the risk of suicide, a Japanese study suggests.
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. The suicide rate was significantly lower in those areas with the highest levels of the element, they wrote in the British Journal of Psychiatry.

So taking about 1/1000 of what someone who need treatment takes could reduce suicide? There is an interesting correlation/causation problem with this study. Is it that the lithium in the water is reducing the suicide rate or could the same thing that reduces suicide increases the lithium amounts? One explanation I have heard is that places where it does not rain much water hangs around longer and rubs off rocks picking up lithium. In places where it rains a lot the lithium levels might be naturally lower as the water does not get a chance to pick up much lithium. The kicker here is that places where it rains all the time might be depressing and that could explain the increased suicide rate.

A quick check of this theory throws up some problems. Oita is in the south of Japan. Oita has 94 days of rain per year . It has Average rainfall of 1677mm

Tokyo where people top themselves at the rate of depressed lemmings at a Leonard Cohen concert also has 94 days of rain per year. 'The city of Hiroshima, in western Honshu, averages a sizeable 1,603 mm (63.1 in) of rain each year. Tokyo, further east near the Pacific, receives an annual average rainfall of 1,460 mm (57.5 in). The city of Sapporo, on Hokkaido, averages 1,158 mm (45.6 in) of precipitation per year. The southern end of the Kii Peninsula is known for a heavy annual rainfall exceeding 4,000 mm (157.5 in).'

A quick back of the envelope is not enough to discout the "rain means less lithium but also more depression" explanation. But I still don't think it is time to put lithium in the drinking water.

Takeshi Terao, a coauthor of the paper and a professor at Oita University.
"I do not think [cities should start adding lithium to the water supply], because our study is a preliminary one and further studies are required to establish evidence."
"Lithium does have its negative side effects as well. Some are mild: people often feel thirsty when taking lithium. Other side effects can be more severe, like weight-gain and diabetes and kidney problems. Lithium in the water supply could increase these side effects as well, although Terao's study didn't examine this possibility. Since the dosages are so much smaller, presumably the side effects would be as well, although more research is needed to prove that."

While on the topic of Lithium 7up used to contain lithium

The product, originally named "Bib-Label Lithiated Lemon-Lime Soda", was launched two weeks before the Wall Street Crash of 1929.[49] It contained the mood stabiliser lithium citrate and was one of a number of patent medicine products popular in the late-19th and early-20th centuries.[50] Its name was soon changed to 7 Up; all American beverage makers were forced to remove lithium in 1948.