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Published in the British Journal of Psychiatry, the study collated research from around the world and found that geographical areas with relatively high levels or concentration of lithium in public drinking water had correspondingly lower suicide rates.

Professor Anjum Memon, Chair in Epidemiology and Public Health Medicine at BSMS and lead author of the study, said: "It is promising that higher levels of trace lithium in drinking water may exert an anti-suicidal effect and have the potential to improve community mental health. The prevalence of mental health conditions and national suicide rates are increasing in many countries. Worldwide, over 800,000 people die by suicide every year, and suicide is the leading cause of death among persons aged 15-24 years."

"In these unprecedented times of COVID-19 pandemic and the consequent increase in the incidence of mental health conditions, accessing ways to improve community mental health and reduce the incidence of anxiety, depression and suicide is ever more important."

Lithium, sometimes referred to as the 'Magic Ion', is widely and effectively used as a medication for the treatment and prevention of manic and depressive episodes, stabilising mood and reducing the risk of suicide in people with mood disorders. Its anti-aggressive properties can help reduce impulsivity, aggression, violent criminal behaviour and chronic substance abuse.

Lithium is a naturally occurring element and is found in variable amounts in vegetables, grains, spices and drinking water. It is present in trace amounts in virtually all rocks, and is mobilised by weathering into soils, ground and standing water, and thus into the public water supply.

The health benefits and curative powers of naturally occurring lithium in water have been known for centuries. The Lithia Springs, an ancient Native American sacred medicinal spring, with its natural lithium-enriched water, is renowned for its health-giving properties. In fact, the popular soft drink 7-Up contained lithium when it was created in 1929.

Recent studies have also linked lithium to reduced incidence of Alzheimer's disease and other dementias. This raises the potential for its preventative use to combat the risk of dementia.

Professor Allan Young, Chair of Mood Disorders at King's College London, said: "This synthesis and analysis of all available evidence confirms previous findings of some individual studies and shows a significant relationship between higher lithium levels in drinking water and lower suicide rates in the community. The levels of lithium in drinking water are far lower than those recommended when lithium is used as medicine although the duration of exposure may be far longer, potentially starting at conception. These findings are also consistent with the finding in clinical trials that lithium reduces suicide and related behaviours in people with a mood disorder."

Professor Memon added: "Next steps might include testing this hypothesis by randomised community trials of lithium supplementation of the water supply, particularly in communities (or settings) with demonstrated high prevalence of mental health conditions, violent criminal behaviour, chronic substance abuse and risk of suicide. This may provide further evidence to support the hypothesis that lithium could be used at the community level to reduce or combat the risk of these conditions."

Professor Carmine Pariante from the Royal College of Psychiatrists, commented: "This study shows that the boundaries between medication and nutritional interventions are not as rigid as we used to think, opening up the possibility of new treatments that span both domains. More knowledge of the beneficial properties of lithium and its role in regulating brain function can lead to a deeper understanding of mental illness and improve the wellbeing of patients with depression and other mental health problems."

The study involved systematic review and meta-analysis of all previous studies on the subject -- conducted in Austria, Greece, Italy, Lithuania, UK, Japan and USA -- which correlated naturally occurring lithium levels in drinking water samples and suicide rates in 1,286 regions/counties/cities in these countries.

Anjum Memon, Imogen Rogers, Sophie M. D. D. Fitzsimmons, Ben Carter, Rebecca Strawbridge, Diego Hidalgo-Mazzei, Allan H. Young. Association between naturally occurring lithium in drinking water and suicide rates: systematic review and meta-analysis of ecological studies. The British Journal of Psychiatry, 2020; 1 DOI: 10.1192/bjp.2020.128

The research team behind the new study, from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), the URI Graduate School of Oceanography, the National Institute of Advanced Industrial Science and Technology, the Kochi University and Marine Works Japan, gathered the ancient sediment samples ten years ago during an expedition to the South Pacific Gyre, the part of the ocean with the lowest productivity and fewest nutrients available to fuel the marine food web.

"Our main question was whether life could exist in such a nutrient-limited environment or if this was a lifeless zone," said the paper's lead author Yuki Morono, senior scientist at JAMSTEC. "And we wanted to know how long the microbes could sustain their life in a near-absence of food."

On the seafloor, there are layers of sediment consisting of marine snow (organic debris continually sourced from the sea surface), dust, and particles carried by the wind and ocean currents. Small life forms such as microbes become trapped in this sediment.

Aboard the research drillship JOIDES Resolution, the team drilled numerous sediment cores 100 meters below the seafloor and nearly 6,000 meters below the ocean's surface. The scientists found that oxygen was present in all of the cores, suggesting that if sediment accumulates slowly on the seafloor at a rate of no more than a meter or two every million years, oxygen will penetrate all the way from the seafloor to the basement. Such conditions make it possible for aerobic microorganisms -- those that require oxygen to live -- to survive for geological time scales of millions of years.

With fine-tuned laboratory procedures, the scientists, led by Morono, incubated the samples to coax their microbes to grow. The results demonstrated that rather than being fossilised remains of life, the microbes in the sediment had survived, and were capable of growing and dividing.

"We knew that there was life in deep sediment near the continents where there's a lot of buried organic matter," said URI Graduate School of Oceanography professor and co-author of the study Steven D'Hondt. "But what we found was that life extends in the deep ocean from the seafloor all the way to the underlying rocky basement."

Morono was initially taken aback by the results. "At first I was sceptical, but we found that up to 99.1% of the microbes in sediment deposited 101.5 million years ago were still alive and were ready to eat," he said.

With the newly developed ability to grow, manipulate and characterise ancient microorganisms, the research team is looking forward to applying a similar approach to other questions about the geological past. According to Morono, life for microbes in the subseafloor is very slow compared to life above it, and so the evolutionary speed of these microbes will be slower. "We want to understand how or if these ancient microbes evolved," he said. "This study shows that the subseafloor is an excellent location to explore the limits of life on Earth."

Before looking ahead to future research, D'Hondt took time to reflect on Morono's achievement. "What's most exciting about this study is that it shows that there are no limits to life in the old sediment of the world's ocean," said D'Hondt. "In the oldest sediment we've drilled, with the least amount of food, there are still living organisms, and they can wake up, grow and multiply."

This study was supported by the Japan Society for the Promotion of Science (JSPS), the Funding Program for Next Generation World-Leading Researchers, and the U.S. National Science Foundation. This study was conducted using core samples collected during Expedition 329, "South Pacific Gyre Subseafloor Life," of the Integrated Ocean Drilling Program.

Morono, Y., Ito, M., Hoshino, T. et al. Aerobic microbial life persists in oxic marine sediment as old as 101.5 million years. Nat Commun, 2020 DOI: 10.1038/s41467-020-17330-1

Plato, the Greek philosopher who lived in the 5th century B.C.E., believed that the universe was made of five types of matter: earth, air, fire, water, and cosmos. Each was described with a particular geometry, a platonic shape. For earth, that shape was the cube.

Science has steadily moved beyond Plato's conjectures, looking instead to the atom as the building block of the universe. Yet Plato seems to have been onto something, researchers have found.

In a new paper in the Proceedings of the National Academy of Sciences, a team from the University of Pennsylvania, Budapest University of Technology and Economics, and University of Debrecen uses math, geology, and physics to demonstrate that the average shape of rocks on Earth is a cube.

"Plato is widely recognised as the first person to develop the concept of an atom, the idea that matter is composed of some indivisible component at the smallest scale," says Douglas Jerolmack, a geophysicist in Penn's School of Arts & Sciences' Department of Earth and Environmental Science and the School of Engineering and Applied Science's Department of Mechanical Engineering and Applied Mechanics. "But that understanding was only conceptual; nothing about our modern understanding of atoms derives from what Plato told us.

"The interesting thing here is that what we find with rock, or earth, is that there is more than a conceptual lineage back to Plato. It turns out that Plato's conception about the element earth being made up of cubes is, literally, the statistical average model for real earth. And that is just mind-blowing."

The group's finding began with geometric models developed by mathematician Gábor Domokos of the Budapest University of Technology and Economics, whose work predicted that natural rocks would fragment into cubic shapes.

"This paper is the result of three years of serious thinking and work, but it comes back to one core idea," says Domokos. "If you take a three-dimensional polyhedral shape, slice it randomly into two fragments and then slice these fragments again and again, you get a vast number of different polyhedral shapes. But in an average sense, the resulting shape of the fragments is a cube."

Domokos pulled two Hungarian theoretical physicists into the loop: Ferenc Kun, an expert on fragmentation, and János Török, an expert on statistical and computational models. After discussing the potential of the discovery, Jerolmack says, the Hungarian researchers took their finding to Jerolmack to work together on the geophysical questions; in other words, "How does nature let this happen?"

"When we took this to Doug, he said, 'This is either a mistake, or this is big,'" Domokos recalls. "We worked backward to understand the physics that results in these shapes."

Fundamentally, the question they answered is what shapes are created when rocks break into pieces. Remarkably, they found that the core mathematical conjecture unites geological processes not only on Earth but around the solar system as well.

"Fragmentation is this ubiquitous process that is grinding down planetary materials," Jerolmack says. "The solar system is littered with ice and rocks that are ceaselessly smashing apart. This work gives us a signature of that process that we've never seen before."

Part of this understanding is that the components that break out of a formerly solid object must fit together without any gaps, like a dropped dish on the verge of breaking. As it turns out, the only one of the so-called platonic forms -- polyhedra with sides of equal length -- that fit together without gaps are cubes.

"One thing we've speculated in our group is that, quite possibly Plato looked at a rock outcrop and after processing or analyzing the image subconsciously in his mind, he conjectured that the average shape is something like a cube," Jerolmack says.

"Plato was very sensitive to geometry," Domokos adds. According to lore, the phrase "Let no one ignorant of geometry enter" was engraved at the door to Plato's Academy. "His intuitions, backed by his broad thinking about science, may have led him to this idea about cubes," says Domokos.

To test whether their mathematical models held true in nature, the team measured a wide variety of rocks, hundreds that they collected and thousands more from previously collected datasets. No matter whether the rocks had naturally weathered from a large outcropping or been dynamited out by humans, the team found a good fit to the cubic average.

However, special rock formations exist that appear to break the cubic "rule." The Giant's Causeway in Northern Ireland, with its soaring vertical columns, is one example, formed by the unusual process of cooling basalt. These formations, though rare, are still encompassed by the team's mathematical conception of fragmentation; they are just explained by out-of-the-ordinary processes at work.

"The world is a messy place," says Jerolmack. "Nine times out of 10, if a rock gets pulled apart or squeezed or sheared -- and usually these forces are happening together -- you end up with fragments which are, on average, cubic shapes. It's only if you have a very special stress condition that you get something else. The earth just doesn't do this often."

The researchers also explored fragmentation in two dimensions, or on thin surfaces that function as two-dimensional shapes, with a depth that is significantly smaller than the width and length. There, the fracture patterns are different, though the central concept of splitting polygons and arriving at predictable average shapes still holds.

"It turns out in two dimensions you're about equally likely to get either a rectangle or a hexagon in nature," Jerolmack says. "They're not true hexagons, but they're the statistical equivalent in a geometric sense. You can think of it like paint cracking; a force is acting to pull the paint apart equally from different sides, creating a hexagonal shape when it cracks."

In nature, examples of these two-dimensional fracture patterns can be found in ice sheets, drying mud, or even the earth's crust, the depth of which is far outstripped by its lateral extent, allowing it to function as a de facto two-dimensional material. It was previously known that the earth's crust fractured in this way, but the group's observations support the idea that the fragmentation pattern results from plate tectonics.

Identifying these patterns in rock may help in predicting phenomenon such as rock fall hazards or the likelihood and location of fluid flows, such as oil or water, in rocks.

For the researchers, finding what appears to be a fundamental rule of nature emerging from millennia-old insights has been an intense but satisfying experience.

"There are a lot of sand grains, pebbles, and asteroids out there, and all of them evolve by chipping in a universal manner," says Domokos, who is also co-inventor of the Gömböc, the first known convex shape with the minimal number -- just two -- of static balance points. Chipping by collisions gradually eliminates balance points, but shapes stop short of becoming a Gömböc; the latter appears as an unattainable end point of this natural process.

The current result shows that the starting point may be a similarly iconic geometric shape: the cube with its 26 balance points. "The fact that pure geometry provides these brackets for a ubiquitous natural process, gives me happiness," he says.

"When you pick up a rock in nature, it's not a perfect cube, but each one is a kind of statistical shadow of a cube," adds Jerolmack. "It calls to mind Plato's allegory of the cave. He posited an idealized form that was essential for understanding the universe, but all we see are distorted shadows of that perfect form."

Gábor Domokos, Douglas J. Jerolmack, Ferenc Kun, János Török. Plato’s cube and the natural geometry of fragmentation. Proceedings of the National Academy of Sciences, 2020; 202001037 DOI: 10.1073/pnas.2001037117