Physicists Aim to Classify All Possible Phases of Matter

A complete classification could lead to a wealth of new materials and technologies. But some exotic phases continue to resist understanding.

In the last three decades, condensed matter physicists have discovered a wonderland of exotic new phases of matter: emergent, collective states of interacting particles that are nothing like the solids, liquids and gases of common experience.

The phases, some realized in the lab and others identified as theoretical possibilities, arise when matter is chilled almost to absolute-zero temperature, hundreds of degrees below the point at which water freezes into ice. In these frigid conditions, particles can interact in ways that cause them to shed all traces of their original identities. Experiments in the 1980s revealed that in some situations electrons split en masse into fractions of particles that make braidable trails through space-time; in other cases, they collectively whip up massless versions of themselves. A lattice of spinning atoms becomes a fluid of swirling loops or branching strings; crystals that began as insulators start conducting electricity over their surfaces. One phase that shocked experts when recognized as a mathematical possibility in 2011 features strange, particle-like “fractons” that lock together in fractal patterns.

Now, research groups at Microsoft and elsewhere are racing to encode quantum information in the braids and loops of some of these phases for the purpose of developing a quantum computer. Meanwhile, condensed matter theorists have recently made major strides in understanding the pattern behind the different collective behaviors that can arise, with the goal of enumerating and classifying all possible phases of matter. If a complete classification is achieved, it would not only account for all phases seen in nature so far, but also potentially point the way toward new materials and technologies.

Led by dozens of top theorists, with input from mathematicians, researchers have already classified a huge swath of phases that can arise in one or two spatial dimensions by relating them to topology: the math that describes invariant properties of shapes like the sphere and the torus. They’ve also begun to explore the wilderness of phases that can arise near absolute zero in 3-D matter.

“It’s not a particular law of physics” that these scientists seek, said Michael Zaletel, a condensed matter theorist at Princeton University. “It’s the space of all possibilities, which is a more beautiful or deeper idea in some ways.” Perhaps surprisingly, Zaletel said, the space of all consistent phases is itself a mathematical object that “has this incredibly rich structure that we think ends up, in 1-D and 2-D, in one-to-one correspondence with these beautiful topological structures.”

In the landscape of phases, there is “an economy of options,” said Ashvin Vishwanath of Harvard University. “It all seems comprehensible” — a stroke of luck that mystifies him. Enumerating phases of matter could have been “like stamp collecting,” Vishwanath said, “each a little different, and with no connection between the different stamps.” Instead, the classification of phases is “more like a periodic table. There are many elements, but they fall into categories and we can understand the categories.”

While classifying emergent particle behaviors might not seem fundamental, some experts, including Xiao-Gang Wen of the Massachusetts Institute of Technology, say the new rules of emergent phases show how the elementary particles themselves might arise from an underlying network of entangled bits of quantum information, which Wen calls the “qubit ocean.” For example, a phase called a “string-net liquid” that can emerge in a three-dimensional system of qubits has excitations that look like all the known elementary particles. “A real electron and a real photon are maybe just fluctuations of the string-net,” Wen said.

A New Topological Order

Before these zero-temperature phases cropped up, physicists thought they had phases all figured out. By the 1950s, they could explain what happens when, for example, water freezes into ice, by describing it as the breaking of a symmetry: Whereas liquid water has rotational symmetry at the atomic scale (it looks the same in every direction), the H20 molecules in ice are locked in crystalline rows and columns.

Things changed in 1982 with the discovery of phases called fractional quantum Hall states in an ultracold, two-dimensional gas of electrons. These strange states of matter feature emergent particles with fractions of an electron’s charge that take fractions of steps in a one-way march around the perimeter of the system. “There was no way to use different symmetry to distinguish those phases,” Wen said.

A new paradigm was needed. In 1989, Wen imagined phases like the fractional quantum Hall states arising not on a plane, but on different topological manifolds — connected spaces such as the surface of a sphere or a torus. Topology concerns global, invariant properties of such spaces that can’t be changed by local deformations. Famously, to a topologist, you can turn a doughnut into a coffee cup by simply deforming its surface, since both surfaces have one hole and are therefore equivalent topologically. You can stretch and squeeze all you like, but even the most malleable doughnut will refuse to become a pretzel.

Wen found that new properties of the zero-temperature phases were revealed in the different topological settings, and he coined the term “topological order” to describe the essence of these phases. Other theorists were also uncovering links to topology. With the discovery of many more exotic phases — so many that researchers say they can barely keep up — it became clear that topology, together with symmetry, offers a good organizing schema.

The topological phases only show up near absolute zero, because only at such low temperatures can systems of particles settle into their lowest-energy quantum “ground state.” In the ground state, the delicate interactions that correlate particles’ identities — effects that are destroyed at higher temperatures — link up particles in global patterns of quantum entanglement. Instead of having individual mathematical descriptions, particles become components of a more complicated function that describes all of them at once, often with entirely new particles emerging as the excitations of the global phase. The long-range entanglement patterns that arise are topological, or impervious to local changes, like the number of holes in a manifold.

Consider the simplest topological phase in a system — called a “quantum spin liquid” — that consists of a 2-D lattice of “spins,” or particles that can point up, down, or some probability of each simultaneously. At zero temperature, the spin liquid develops strings of spins that all point down, and these strings form closed loops. As the directions of spins fluctuate quantum-mechanically, the pattern of loops throughout the material also fluctuates: Loops of down spins merge into bigger loops and divide into smaller loops. In this quantum-spin-liquid phase, the system’s ground state is the quantum superposition of all possible loop patterns.

To understand this entanglement pattern as a type of topological order, imagine, as Wen did, that the quantum spin liquid is spilling around the surface of a torus, with some loops winding around the torus’s hole. Because of these hole windings, instead of having a single ground state associated with the superposition of all loop patterns, the spin liquid will now exist in one of four distinct ground states, tied to four different superpositions of loop patterns. One state consists of all possible loop patterns with an even number of loops winding around the torus’s hole and an even number winding through the hole. Another state has an even number of loops around the hole and an odd number through the hole; the third and fourth ground states correspond to odd and even, and odd and odd, numbers of hole windings, respectively.

Which of these ground states the system is in stays fixed, even as the loop pattern fluctuates locally. If, for instance, the spin liquid has an even number of loops winding around the torus’s hole, two of these loops might touch and combine, suddenly becoming a loop that doesn’t wrap around the hole at all. Long-way loops decrease by two, but the number remains even. The system’s ground state is a topologically invariant property that withstands local changes.

Future quantum computers could take advantage of this invariant quality. Having four topological ground states that aren’t affected by local deformations or environmental error “gives you a way to store quantum information, because your bit could be what ground state it’s in,” explained Zaletel, who has studied the topological properties of spin liquids and other quantum phases. Systems like spin liquids don’t really need to wrap around a torus to have topologically protected ground states. A favorite playground of researchers is the toric code, a phase theoretically constructed by the condensed matter theorist Alexei Kitaev of the California Institute of Technology in 1997 and demonstrated in experiments over the past decade. The toric code can live on a plane and still maintain the multiple ground states of a torus. (Loops of spins are essentially able to move off the edge of the system and re-enter on the opposite side, allowing them to wind around the system like loops around a torus’s hole.) “We know how to translate between the ground-state properties on a torus and what the behavior of the particles would be,” Zaletel said.

Spin liquids can also enter other phases, in which spins, instead of forming closed loops, sprout branching networks of strings. This is the string-net liquid phase that, according to Wen, “can produce the Standard Model” of particle physics starting from a 3-D qubit ocean.

The Universe of Phases

Research by several groups in 2009 and 2010 completed the classification of “gapped” phases of matter in one dimension, such as in chains of particles. A gapped phase is one with a ground state: a lowest-energy configuration sufficiently removed or “gapped” from higher-energy states that the system stably settles into it. Only gapped quantum phases have well-defined excitations in the form of particles. Gapless phases are like swirling matter miasmas or quantum soups and remain largely unknown territory in the landscape of phases.

For a 1-D chain of bosons — particles like photons that have integer values of quantum spin, which means they return to their initial quantum states after swapping positions — there is only one gapped topological phase. In this phase, first studied by the Princeton theorist Duncan Haldane, who, along with David Thouless and J. Michael Kosterlitz, won the 2016 Nobel Prize for decades of work on topological phases, the spin chain gives rise to half-spin particles on both ends. Two gapped topological phases exist for chains of fermions — particles like electrons and quarks that have half-integer values of spin, meaning their states become negative when they switch positions. The topological order in all these 1-D chains stems not from long-range quantum entanglement, but from local symmetries acting between neighboring particles. Called “symmetry-protected topological phases,” they correspond to “cocycles of the cohomology group,” mathematical objects related to invariants like the number of holes in a manifold.

 Two-dimensional phases are more plentiful and more interesting. They can have what some experts consider “true” topological order: the kind associated with long-range patterns of quantum entanglement, like the fluctuating loop patterns in a spin liquid. In the last few years, researchers have shown that these entanglement patterns correspond to topological structures called tensor categories, which enumerate the different ways that objects can possibly fuse and braid around one another. “The tensor categories give you a way [to describe] particles that fuse and braid in a consistent way,” said David Pérez-García of Complutense University of Madrid.

Researchers like Pérez-García are working to mathematically prove that the known classes of 2-D gapped topological phases are complete. He helped close the 1-D case in 2010, at least under the widely-held assumption that these phases are always well-approximated by quantum field theories — mathematical descriptions that treat the particles’ environments as smooth. “These tensor categories are conjectured to cover all 2-D phases, but there is no mathematical proof yet,” Pérez-García said. “Of course, it would be much more interesting if one can prove that this is not all. Exotic things are always interesting because they have new physics, and they’re maybe useful.”

Gapless quantum phases represent another kingdom of possibilities to explore, but these impenetrable fogs of matter resist most theoretical methods. “The language of particles is not useful, and there are supreme challenges that we are starting to confront,” said Senthil Todadri, a condensed matter theorist at MIT. Gapless phases present the main barrier in the quest to understand high-temperature superconductivity, for instance. And they hinder quantum gravity researchers in the “it from qubit” movement, who believe that not only elementary particles, but also space-time and gravity, arise from patterns of entanglement in some kind of underlying qubit ocean. “In it from qubit, we spend much of our time on gapless states because this is where one gets gravity, at least in our current understanding,” said Brian Swingle, a theoretical physicist at the University of Maryland. Some researchers try to use mathematical dualities to convert the quantum-soup picture into an equivalent particle description in one higher dimension. “It should be viewed in the spirit of exploring,” Todadri said.

Even more enthusiastic exploration is happening in 3-D. What’s already clear is that, when spins and other particles spill from their chains and flatlands and fill the full three spatial dimensions of reality, unimaginably strange patterns of quantum entanglement can emerge. “In 3-D, there are things that escape, so far, this tensor-category picture,” said Pérez-García. “The excitations are very wild.”

The Haah Code

The very wildest of the 3-D phases appeared seven years ago. A talented Caltech graduate student named Jeongwan Haah discovered the phase in a computer search while looking for what’s known as the “dream code”: a quantum ground state so robust that it can be used to securely store quantum memory, even at room temperature.

For this, Haah had to turn to 3-D matter. In 2-D topological phases like the toric code, a significant source of error is “stringlike operators”: perturbations to the system that cause new strings of spins to accidentally form. These strings will sometimes wind new loops around the torus’s hole, bumping the number of windings from even to odd or vice versa and converting the toric code to one of its three other quantum ground states. Because strings grow uncontrollably and wrap around things, experts say there cannot be good quantum memories in 2-D.

Jeongwan Haah, a condensed matter theorist now working at Microsoft Research in Redmond, Washington, discovered a bizarre 3-D phase of matter with fractal properties.

Jeongwan Haah, a condensed matter theorist now working at Microsoft Research in Redmond, Washington, discovered a bizarre 3-D phase of matter with fractal properties.


Haah wrote an algorithm to search for 3-D phases that avoid the usual kinds of stringlike operators. The computer coughed up 17 exact solutions that he then studied by hand. Four of the phases were confirmed to be free of stringlike operators; the one with the highest symmetry was what’s now known as the Haah code.

As well as being potentially useful for storing quantum memory, the Haah code was also profoundly weird. Xie Chen, a condensed matter theorist at Caltech, recalled hearing the news as a graduate student in 2011, within a month or two of Haah’s disorienting discovery. “Everyone was totally shocked,” she said. “We didn’t know anything we could do about it. And now, that’s been the situation for many years.”

The Haah code is relatively simple on paper: It’s the solution of a two-term energy formula, describing spins that interact with their eight nearest neighbors in a cubic lattice. But the resulting phase “strains our imaginations,” Todadri said.

The code features particle-like entities called fractons that, unlike the loopy patterns in, say, a quantum spin liquid, are nonliquid and locked in place; the fractons can only hop between positions in the lattice if those positions are operated upon in a fractal pattern. That is, you have to inject energy into the system at each corner of, say, a tetrahedron connecting four fractons in order to make them switch positions, but when you zoom in, you see that what you treated as a point-like corner was actually the four corners of a smaller tetrahedron, and you have to inject energy into the corners of that one as well. At a finer scale, you see an even smaller tetrahedron, and so on, all the way down to the finest scale of the lattice. This fractal behavior means that the Haah code never forgets the underlying lattice it comes from, and it can never be approximated by a smoothed-out description of the lattice, as in a quantum field theory. What’s more, the number of ground states in the Haah code grows with the size of the underlying lattice — a decidedly non-topological property. (Stretch a torus, and it’s still a torus.)

The quantum state of the Haah code is extraordinarily secure, since a “fractal operator” that perfectly hits all the marks is unlikely to come along at random. Experts say a realizable version of the code would be of great technological interest.

Haah’s phase has also generated a surge of theoretical speculation. Haah helped matters along in 2015 when he and two collaborators at MIT discovered many examples of a class of phases now known as “fracton models” that are simpler cousins of the Haah code. (The first model in this family was introduced by Claudio Chamon of Boston University in 2005.) Chen and others have since been studying the topology of these fracton systems, some of which permit particles to move along lines or sheets within a 3-D volume and might aid conceptual understanding or be easier to realize experimentally. “It’s opening the door to many more exotic things,” Chen said of the Haah code. “It’s an indication about how little we know about 3-D and higher dimensions. And because we don’t yet have a systematic picture of what is going on, there might be a lot of things lying out there waiting to be explored.

No one knows yet where the Haah code and its cousins belong in the landscape of possible phases, or how much bigger this space of possibilities might be. According to Todadri, the community has made progress in classifying the simplest gapped 3-D phases, but more exploration is needed in 3-D before a program of complete classification can begin there. What’s clear, he said, is that “when the classification of gapped phases of matter is taken up in 3-D, it will have to confront these weird possibilities that Haah first discovered.”

Many researchers think new classifying concepts, and even whole new frameworks, might be necessary to capture the Haah code’s fractal nature and reveal the full scope of possibilities for 3-D quantum matter. Wen said, “You need a new type of theory, new thinking.” Perhaps, he said, we need a new picture of nonliquid patterns of long-range entanglement. “We have some vague ideas but don’t have a very systematic mathematics to do them,” he said. “We have some feeling what it looks like. The detailed systematics are still lacking. But that’s exciting.”

Foods with Fructose Linked to High Blood Pressure.

As if you needed any other reason to reduce sugar intake, a study found that the over-consumption of foods with fructose is linked to high blood pressure. Not surprisingly, giant groups who want you to eat more HFCS (the worst kind of sugar) have spoken out against this and other similar studies.

applecause 235x147 Foods with Fructose Linked to High Blood Pressure

Fructose is a natural sugar found in fruit and vegetables, as well as many processed foods containing high-fructose corn syrup. What’s unnatural about it all is the sheer volume of fructose we find in foods in the form of HFCS and just how much of this sweet syrup Americans are taking in.

In the 1950s and 1960s, sucrose was the main source of sugar for Americans. Sucrose is the sweet substance in table sugar made from sugarcane or beets. But with the development of cheap HFCS, that changed dramatically.

Research shows that Americans consume 35 pounds of high-fructose corn syrup each year, although according to Princeton University, the average American consumes 60 pounds of HFCS every single year.

This most recent study found that those participants who took in 74 grams of fructose (the equivalent of about 2.5 sweet drinks), were at a 28% greater risk of blood pressure levels 135/85 or higher and a 77% greater risk of extreme high blood pressure, with levels greater than 160/100.

Soon after the findings were published, the Corn Refiners Association spoke out saying that the researchers overestimated the amount of fructose in the drinks being studied. The researchers denied this.

The American Beverage Association also weighed in, saying the findings, “furthers the confusion and misunderstandings about high fructose corn syrup and sugar-sweetened beverages,” adding that no cause and effect relationship could be established through this particular research methodology.

The researchers agree, to a certain extent, and admit that further research is needed in order to say for certain that foods with fructose caused the high blood pressure and weren’t simply a contributor or linked.



Super-Earth Planet Is More Like Super-Venus, NASA Says.

An alien planet declared a super-Earth by NASA might not be so habitable after all. New measurements flag the planet (called Kepler-69c) as more of a “super-Venus” that would likely be inhospitable to life.

The planetary status change is part of a larger struggle over how to define the habitable zone of a star. In recent years, scientists determined that the distance between a planet and its type of star is just one metric that hints at the likelihood of liquid water on its surface, which could fuel life. Other factors include the planet’s atmosphere and even how the star behaves.

Super-Venus and Super-Earth

“There are a lot of unanswered questions about habitability,” astrophysicist Lucianne Walkowicz, Kepler science team member at Princeton University, said in a statement.

“If the planet gets zapped with radiation all the time by flares from its parent star, the surface might not be a very pleasant place to live. But on the other hand, if there’s liquid water around, that makes a really good shield from high-energy radiation, so maybe life could thrive in the oceans.”

Kepler-69c was, as its name suggests, discovered using the planet-hunting Kepler space telescope. NASA announced the find in April, declaring that the planet is about 1.7 times Earth’s size and “orbits in the habitable zone of a star similar to our sun.” A closer look at the planet’s chemistry, however, showed the planet is actually just outside the habitable zone’s inner edge.

“For example, molecules in a planet’s atmosphere will absorb a certain amount of energy from starlight and radiate the rest back out,” NASA said in a follow-up press release in June. “How much of this energy is trapped can mean the difference between a turquoise sea and erupting volcanoes.”

The researchers also took the star’s energy output and Kepler-69c‘s orbit into account when making the determination. It’s still hard to say for sure if the planet is in the habitable zone, however. A next step could be to look at the atmosphere of the planet itself, but it is difficult for current telescopes to pick up the “signatures” of water, oxygen, carbon dioxide or methane that could indicate life.

Even though the James Webb Space Telescope — slated to launch in 2018 — can examine planetary atmospheres, its capabilities are designed for planets that are far larger than Earth. Probing the atmosphere of Kepler-69c may have to wait for a more sensitive telescope, NASA said.

Soda Linked to Aggression, Attention Problems, and Social Withdrawal in Young Children.

Soda has already been blamed for making kids obese. New research blames the sugary drinks for behavioral problems in children too.

Analyzing data from 2,929 families, researchers linked soda consumption to aggression, attention problems and social withdrawal in 5-year-olds. They published their findings in the Journal of Pediatrics on Friday.

Although earlier studies have shown an association between soft-drink consumption and aggression in teens, none had investigated whether a similar relationship existed in younger children.

To that end, Columbia University epidemiologist Shakira Suglia and her colleagues examined data from the Fragile Families and Child Wellbeing Study, which followed 2,929 mother-child pairs in 20 large U.S. cities from the time the children were born. The study, run by Columbia and Princeton University, collected information through surveys the mothers completed periodically over several years.

In one survey, mothers answered questions about behavior problems in their children. They also reported how much soda their kids drank on a typical day.

Suglia and her colleagues found that even at the young age of 5, 43% of the kids consumed at least one serving of soda per day, and 4% drank four servings or more.

The more soda kids drank, the more likely their mothers were to report that the kids had problems with aggression, withdrawal and staying focused on a task. For instance, children who downed four or more servings of soda per day were more than twice as likely to destroy others’ belongings, get into fights and physically attack people, compared with kids who didn’t drink soda at all.


How Exercise Can Calm Anxiety.

Story at-a-glance

  • A new study revealed that exercising creates new, excitable neurons along with new neurons designed to release the GABA neurotransmitter, which inhibits excessive neuronal firing, helping to induce a natural state of calm
  • While the creation of excitable neurons via exercise would ordinarily induce anxiety, exercise fixes this problem by also creating calm-inducing GABA-releasing neurons
  • The mood-boosting benefits of exercise occur both immediately after a workout and continue on in the long term
  • In addition to the creation of new neurons, including those that release the calming neurotransmitter GABA, exercise boosts levels of potent brain chemicals like serotonin, dopamine, and norepinephrine, which may help buffer some of the effects of stress

Exercise is known to create new excitable neurons in the hippocampus, an area of the brain involved in thinking and emotions.

This would suggest that exercise might induce anxiety in physically active people, but, ironically, research shows that exercise is associated with reduced anxiety and calmness.

The reason for these seemingly incompatible exercise effects was recently explored by Princeton University, who appear to have revealed, as the New York Times put it, “an eye-opening demonstration of nature’s ingenuity.”1

Exercise Creates New Excitable Brain Cells… and Quiets Them When Necessary

Newly formed ‘young’ neurons can be prone to easy excitement, making them quite efficient at inducing anxiety. Physical exercise creates excitable new neurons in abundance, which is beneficial in the long run, but would be expected to increase anxiety rates in the short term.

However, a new animal study comparing running mice with sedentary mice found that while the exercising animals’ brains ‘teemed with many new, excitable neurons,’ they also contained new neurons designed to release a neurotransmitter called gamma-aminobutyric acid (GABA). GABA inhibits excessive neuronal firing.

This helps to induce a natural state of calm.2 Commonly prescribed anti-anxiety drugs like Ativan, Xanax and Valium actually exert a calming effect in this same manner, by boosting the action of GABA.

Exercise appears to go one step further, however, as when the mice were later exposed to a stressful situation, the study found that the exercising mice, as opposed to the sedentary mice, responded with only an initial rush of anxiety, followed by calm. What all of this suggests, one of the study’s authors noted:3

 “ … is that the hippocampus of runners is vastly different from that of sedentary animals. Not only are there more excitatory neurons and more excitatory synapses, but the inhibitory neurons are more likely to become activated, presumably to dampen the excitatory neurons, in response to stress.

… I think it’s not a huge stretch to suggest that the hippocampi of active people might be less susceptible to certain undesirable aspects of stress than those of sedentary people.”

Exercise Can Be a Key Anti-Anxiety Treatment

Some psychologists swear by exercise as a primary form of treatment for depression, anxiety and other mood disorders. Research has shown again and again that patients who follow regular exercise regimens see improvement in their mood — improvements comparable to that of those treated with medication.

The results really are impressive when you consider that exercise is virtually free and can provide you with numerous other health benefits too. The benefits to your mood occur whether the exercise is voluntary or forced, so even if you feel youhave to exercise, say for health reasons, there’s a good chance you’ll still benefit.

For instance, researchers at the University of Colorado Boulder devised an animal study to determine whether rats that were forced to exercise would experience the same stress and anxiety-reduction as those who were free to choose if and when to exercise.4

The rats exercised either voluntarily or forcibly for six weeks, after which they were exposed to a stressor. The following day, their anxiety levels were tested by measuring how long they froze when placed in an environment they’d been conditioned to fear. The longer the rats remained frozen, like “a deer in headlights,” the greater the residual anxiety from the previous day’s stressor. According to the lead author:5

“Regardless of whether the rats chose to run or were forced to run they were protected against stress and anxiety. The sedentary rats froze for longer periods of time than any of the active rats. The implications are that humans who perceive exercise as being forced — perhaps including those who feel like they have to exercise for health reasons — are maybe still going to get the benefits in terms of reducing anxiety and depression.”

What Type of Exercise Is Best for Anxiety?

If you struggle with anxiety, you really can’t go wrong with starting a comprehensive exercise program – virtually any physical activity is likely to have positive effects, especially if it’s challenging enough. That said, Duke University researchers recently published a review of more than 100 studies that found yoga appears to be particularly beneficial for mental health.6 Lead author Dr. P. Murali Doraiswamy, a professor of psychiatry and medicine at Duke University Medical Center told Time Magazine:7

“Most individuals already know that yoga produces some kind of a calming effect. Individually, people feel better after doing the physical exercise. Mentally, people feel calmer, sharper, maybe more content. We thought it’s time to see if we could pull all [the literature] together… to see if there’s enough evidence that the benefits individual people notice can be used to help people with mental illness.”

According to their findings, yoga appears to have a positive effect on:

  • Mild depression
  • Sleep problems
  • Schizophrenia (among patients using medication)
  • ADHD (among patients using medication)

Some of the studies in the review suggested yoga can have a similar effect to antidepressants and psychotherapy, by influencing neurotransmitters and boosting serotonin. Separate research also found that three months of regular yoga sessions resulted in less anxiety and depression, with anxiety scores falling from an average of 34 (on a scale of 20-80) to an average of 25.

However, while recent studies support the use of yoga to improve common psychiatric disorders (along with providing many other health benefits, such as promoting flexibility and core muscles, alleviating back pain, and more), I think it’s important to incorporate a variety of exercises into your routine for optimal health results. Ideally, you’ll want a comprehensive fitness programthat high-intensity interval training like Peak Fitness and resistance training as well, in addition to flexibility and core-building exercises like yoga or Foundation Training.

The Mood-Boosting Benefits of Exercise Are Both Immediate and Long-Term

Rather than viewing exercise as a medical tool to lose weight, prevent disease, and live longer – all benefits that occur in the future – try viewing exercise as a daily tool to immediately enhance your frame of mind, reduce stress and feel happier. One study found, for instance, that while many people started an exercise program to lose weight and improve their appearance, theycontinued to exercise because of the benefits to their well-being.8

In addition to the creation of new neurons, including those that release the calming neurotransmitter GABA, exercise boosts levels of potent brain chemicals like serotonin, dopamine, and norepinephrine, which may help buffer some of the effects of stress. Many avid exercisers also feel a sense of euphoria after a workout, sometimes known as the “runner’s high.” It can be quite addictive, in a good way, once you experience just how good it feels to get your heart rate up and your body moving.

Best of all, these mood-boosting benefits are both immediate and long-term. The featured study found that the exercising mice still responded with increased calm even when they hadn’t exercised for 24 hours.

“The runners’ wheels had been locked for 24 hours before their [stress-inducing] cold bath, so they would gain no acute calming effect from exercise. Instead, the difference in stress response between the runners and the sedentary animals reflected fundamental remodeling of their brains,” the New York Times reported.9

What does this mean for you? Adding a regular exercise program to your life is likely to make you feel good each time you exercise plus enhance your mood, lessen anxiety and induce more feelings of calm in the future, too.