A Tufts psychology professor and Harvard Medical School lecturer has recommended dosing US water supplies with the lithium in order to reduce suicide rates, saving an estimated 15,000 - 25,000 lives per year.

Appearing on the Vox podcast "Future Perfect," psychiatrist and researcher Dr. Nassir Ghaemi, MD explains that a 2014 review he co-authored analyzing five studies concluded that areas of the country with higher levels of naturally occurring lithium in the water supply had lower suicide rates. Areas with particularly high concentrations have as much as a 50 to 60 percent reduction.

"In general, in the United States, lithium levels are much higher in the Northeast and East Coast and very low in the Mountain West," Ghaemi told Vox, adding "And suicide rates track that exactly — much lower suicide rates in the Northeast, and the highest rates of suicide are in the Mountain West."

If you apply that 50 to 60 percent reduction to the US, where about 45,000 people total died by suicide in 2016, you get a total number of lives saved at around 22,500 to 27,000 a year. That’s likely too high, since you can’t reduce suicide rates in places that are already high-lithium. Ghaemi’s own back-of-the-envelope calculation is that we’d save 15,000 to 25,000.

Ghaemi and a number of other eminent psychiatrists are making a pretty remarkable claim. They think we could save tens of thousands of lives a year with a very simple, low-cost intervention: putting small amounts of lithium, amounts likely too small to have significant side effects, into our drinking water, the way we put fluoride in to protect our teeth. -Vox

Experts don't agree

While Ghaemi is confident in the life-saving effects of making everybody comfortably numb, several other studies have placed the possible positive effects at minimal to nil. 

In 2015, the Open Philanthropy Project, a large-scale grantmaking group in San Francisco, shared an analysis with me implying that if two specific studies were right, a “small increase in the amount of trace lithium in drinking water in the U.S. could prevent > 4,000 suicides per year.” That’s significant, but far short of 15,000 to 25,000.

And while Ghaemi is very enthusiastic about the potential of groundwater lithium, other researchers are more wary. A comprehensive list of lithium studies, updated just last month, shows that while many studies find positive effects, plenty more found no impact on suicide or other important outcomes. In particular, a large-scale Danish study released in 2017 found “no significant indication of an association between increasing … lithium exposure level and decreasing suicide rate.” -Vox

In response to the new studies, the Open Philanthropy Project has said that the Danish study "makes us substantially less optimistic" that trace amounts of lithium actually reduce suicides. Meanwhile, another study using health care claims in teh US found that more lithium in the water doesn't translate to lower diagnoses of dimentia or bipolar disorder.  

That said, Vox's Dylan Matthews writes: "At the very least, I’d love for some governments to conduct real, bona fide experiments on lithium. Maybe a state could randomly add lithium to some of its reservoirs but not others, or, conversely, a high-lithium state could try removing it from the water. There are serious ethical questions about doing experiments like this that affect whole populations, but if lithium’s effect is real and we don’t pursue it because we lack compelling enough evidence, thereby endangering thousands of people — that’s an ethical problem too.

In other words, we should go ahead and just try dosing a few populations to see what happens!