In "Homeland," Carrie is prescribed lithium, but she doesn't like it. Frank Ockenfels 3/Showtime Lithium has quite the reputation.

As a psychiatric medication it's generally used to treat extreme cases of bipolar disorder and depression in patients who don't respond to traditional antidepressants.

In pop culture, it's represented as having powerful dulling effects.

Carrie Mathison, Claire Danes's character on "Homeland," doesn't like taking the lithium she's prescribed because she thinks it dulls her perceptive abilities. The Nirvana song "Lithium" compares the medication to religion-as-coping-mechanism, something troubled people rely on to get by. In the movie "Silver Linings Playbook," Bradley Cooper's character says he stopped taking his lithium (and other meds) because they make him feel foggy.

These representations aren't fully accurate — lithium can be a lifesaver — but some patients do complain that the medication dulls mental clarity, and the NIH has a long list of lithium's potential side effects, some rather serious.

Still, all of this ignores one fascinating fact: many people unintentionally ingest a very low dose of lithium every day, and some research suggests those people may be better off because of that.

According to that research, people who regularly naturally consume trace amounts of lithium are less likely to commit suicide and less likely to suffer from dementia.

Lithium is a naturally occurring element (not a concoction made in a lab that can be patented and sold). In some parts of the world, including parts of the US, it's found in the drinking water.

Lithium is the lightest metal. 2012rc/Wikimedia Commons In drinking water it's generally present only in incredibly tiny doses — on the high end that concentration is around .170 milligrams of lithium in a liter of water, which is less than a thousandth of the minimum pharmaceutical dose, according to Anna Fels, a psychiatrist and professor at Weill Cornell Medical College, in an article she wrote about lithium in drinking water for the New York Times in September.

Still, even in those tiny doses, it seems that there may be some measurable effect.

Fels writes:

Although it seems strange that the microscopic amounts of lithium found in groundwater could have any substantial medical impact, the more scientists look for such effects, the more they seem to discover. Evidence is slowly accumulating that relatively tiny doses of lithium can have beneficial effects. They appear to decrease suicide rates significantly and may even promote brain health and improve mood.

We'll talk about what the research says about lithium in drinking water in a moment, but first let's clarify that none of this is a reason to go add lithium into your diet (or your town's water supply). The doses in most supplements and prescriptions are more than a thousand times as large as the doses that naturally exist out there, and should only be taken upon consultation with a doctor. In the 1940s, lithium supplements became popular, but the high doses that people ingested had toxic effects, some of which killed people.

Don't try this at home.

Fels argues that what we do know about lithium is so promising that it could potentially be considered an "essential trace element nutrient," a natural nutrient like sodium or iodine that is required for proper human development in some way (in 1996, the World Health Organization classified lithium as a potentially toxic element that may have essential properties).

In theory, there's an argument in that case that lithium should be added to drinking water like flouride, though only in those miniscule quantities that may be beneficial.

But still, the idea of giving everyone low doses of what we use as a powerful mood-stabilizing psychotropic drug to make them happier has a terrifying, science fiction-y dystopian future feel to it.

On the other hand, if this natural element found on earth is actually as neuro-protective as some research seems to suggest, adding it to drinking water could be extremely beneficial in staving off depression and dementia, two outsize medical problems of the modern era.

A lot more research is needed, but here's what we know so far.

Fels cites a number of studies in the Times, and a quick search of the medical literature on studies involving humans who ingest lithium in drinking water comes up with more than 75 results. Even when researchers control for external factors like income and access to healthcare, that doesn't mean that lithium is necessarily responsible for fascinating results like lower suicide rates — but those results are still intriguing.

When looking at the connection between lithium in drinking water and suicide rates, there are mostly positive results:

This is powerful evidence, but it doesn't mean that all research supports adding lithium to drinking water. Some researchers who studied 47 subdivisions in the east of England found no correlation between lithium levels and suicide rates.

And the authors of the larger study in Texas note a few other caveats too. Most researchers who evaluate natural lithium levels in tap water can't necessarily account for lithium consumed in food or bottled water, and they aren't sure how lithium prescriptions affect the levels in drinking water. That could cause the amount of lithium that people are consuming in drinking water to vary from the amount that's naturally in a water supply.

Also, even if lithium definitely lowered suicide and dementia rates, that doesn't mean it couldn't have other negative effects simultaneously. The authors of the large Texas study particularly caution that we have no idea how that supplement would affect pregnant women, thyroid function, and fetuses in utero.

Research into those questions has found negative effects from lithium:

Heavy exposure to lithium and other metals in the Andes has been associated with a detrimental effect on thyroid function.

At least in mice, early exposure to lithium has been linked to slower development.

Obviously, more research is needed before any changes should be made.

But we should maybe reconsider how we understand this controversial element. "Lithium is, by far, the most proven drug to keep neurons alive," Nassir Ghaemi, a Tufts psychiatrist, told Fels. "If lithium prevents dementia, then we may have overlooked a very simple means of preventing a major public health problem."

We don't yet know if that's true, but there's enough evidence, Fels argues, to seriously investigate that possibility. "Research on a simple element like lithium that has been around as a medication for over half a century and as a drink for millenniums may not seem like a high priority," she writes, "but it should be."