How yoga changes the brain

Yoga is more than a trend; yoga is a movement. The practice, imported from India, has become a popular sport in the West. In Germany, more than 15 million people now do the sun salutation, stretch their legs into the downward-looking dog or sit meditatively side by side in the lotus position to relax, manage stress, strengthen their backs and stay fit. Or are at least interested in embarking on the gentle path to well-being. The multitude of practicing expects an improvement of the physical condition as well as the psyche. And this is not a perceived truth.

Physicians and psychotherapists have been investigating the healing effects of yoga for decades. As early as 1956, the neurologist Mariella Fischer-Williams reported on a patient who relieved his chronic pain by practicing yoga - and was ultimately allegedly even completely pain-free. Now a single case alone says nothing. But in 1975, a comprehensive study followed in the journal "The Lancet." The team of authors showed that yoga lowered high blood pressure more than mere relaxation. Even memory is trained by yoga. And the exercises are also said to help with depression, anxiety, and chronic pain.

But what is the reason for this? To find out, scientists and researchers are increasingly focusing on the brain. They push test subjects into the tube of a magnetic resonance imaging (MRI) scanner, measure brain regions and examine how yoga changes electrical voltages of the thinking and control organ. This should yield results that are as objective as possible. For a good reason: Scientifically investigating yoga is quite problematic.

"Whether traditional Hatha, vinyasa with techno beats or sweaty Bikram - they all change our brain"

(Ulrich Ott, psychologist)

Yoga can be athletic or extremely calm

"First of all, there is the question of definition," reports Holger Cramer, head of research at the Clinic for Naturopathy at the Evangelische Kliniken Essen-Mitte. Classically, yoga includes a combination of intensive stretching exercises and poses, the asanas, as well as various procedures of relaxation and meditation, called samyama. The breath, pranayama, is also very important. In yoga, it is considered the link between body and mind and is supposed to help remove the "veil that covers inner enlightenment," as it says in the Yogasutra, a kind of manifesto of yoga.

Over time, however, different styles have emerged, and each sets its own focus: Hatha and Iyengar yoga consist mainly of stretches and restorative poses, while Ashtanga and Vinyasa tend to be more dynamic, include more athletic elements, and in some places even take place accompanied by techno beats. In addition, Bikram. This includes 26 postures that are repeated twice in a 38-degree room. Sweating is inevitable, whereas in Yin Yoga you hardly move at all. It's all about slow stretching as well as meditation.

"What exactly 'yoga' is, accordingly, is hard to say," Cramer says. Moreover, when study participants report feeling better after class, it begs the question: what actually made them feel better? Was it the physical exercises, the focus on the breath? Might it be the feeling of being part of a larger group, or was it the teacher's particular style? All factors, so-called confounders, that complicate yoga research.

The best way to get started with yoga

First and foremost: "Put perfectionism aside and free yourself from any claim that you have to perform the exercises perfectly," advises psychologist Ulrich Ott. Yoga is not about performance, he says, but about developing awareness of one's own body, emotions, and mind. The postures develop their full effect by being performed with conscious breathing and full attention. "Only go as far as you can still breathe calmly," emphasizes the yoga expert. If you hold your breath or breathe very hard, that's a sign that you're overexerting yourself, he says. It is also important to warm up before the individual exercises - which are done, among other things, during the sun salutation.

So now for a look at the brain. This much can already be said at the outset: "Whether traditional Hatha, Vinyasa with techno beats or sweaty Bikram - they all change our brain," notes Ulrich Ott, a psychologist at the Bender Institute of Neuroimaging at Justus Liebig University in Giessen: "Because the various body postures, breathing exercises and meditations are usually practiced repeatedly over long periods of time." And our thought organ generally responds to repeated practice with functional and structural adaptations, he said. That is, the brain regions that are used differentiate and the synaptic connections become stronger. It's comparable to a muscle that gains strength through regular exercise.

"However, this finding is not sensational," neuroscientist Ott points out: "Every hobby that a person pursues over a long period of time changes the brain: reading just like riding a bike." That makes it all the more important to take a closer look at the changes that yoga brings about, he says.

The gray matter of the brain lasts longer

A good overview of the state of neuroscience research is provided by two papers published in 2019. To get around the difficult question of definition, they focus on the three basic elements of all yoga styles: the physical postures of asana, meditation, and breathing exercises. Each of the three components affects the brain differently. The teams measured the changes mostly with structural MRI scans. Many studies also include a series of cognitive and motor tests.

Yoga has a strong effect on gray matter volume, for example. Composed primarily of nerve cell bodies, the substantia grisea is an essential part of the central nervous system and declines over the course of a person's life. Less gray matter impairs memory and could increase the risk of dementia, among other things. Yoga appears to slow this age-related decline, if not provide for the formation of new nerve cell bodies.

Yoga practitioners also performed better in memory, attention, and motor exercises. This is probably because the altered brain areas are primarily responsible for cognitive control, the coordination of movements, and the evaluation of decisions, the study authors explain. For example, beta waves, which are associated with cognitive performance, are particularly active after breathing-based yoga.

In another experiment, researchers from the U.S. subjected people who practiced yoga and others to the Stroop test: They showed them pictures with different colored words, and the subjects had to name the colors of the words presented. Errors in the experiment usually occur with color words that do not correspond to their print color. So if the word is to be read out in blue, although it was printed in green. The result: Those who did yoga not only did better on the test, the MRI also showed that during the experiment the dorsolateral prefrontal cortex (DLPFC) was particularly active, while the amygdala was hardly active at all.

In addition, yoga can help to better perceive and regulate emotions, the study authors write. This supports the thesis: Yoga practitioners exhibit a higher frequency of alpha waves after meditation, breathing exercises, and asanas. These brain waves are relatively slow and put the brain into a state of rest in which it vibrates more leisurely and can thus absorb more.

And that's not all. In a part of the forebrain called the ventral striatum, the neurotransmitter dopamine increases sharply during meditation exercises. This has been shown by neurophysiological studies on highly experienced male yoga practitioners. Dopamine is an endogenous mood enhancer and stimulates important cognitive processes in the prefrontal cortex. When dopamine levels drop, attention, concentration, and other mental abilities usually decline. Many studies also report a decrease in stress response. According to these, an eight-week hatha yoga program lowers blood levels of the stress hormone cortisol significantly more than stretching. The yoga practitioners also learned faster and performed better on accuracy tests. But the researchers have not yet been able to figure out how this works in detail.

"It is also possible, after all, that the long-term yogis already had a larger brain volume before they started practicing"

(Holger Cramer, medical scientist)

First neurological changes already after 20 minutes?

So there is plenty of evidence that yoga changes our brains. But are the changes lasting? Is it enough to go to the studio once a week, or does it take years of training? "We can't say conclusively so far," says medical scientist Cramer. The research situation is not clear on the dose and duration, even though there are many indications that even short-term practice affects.

Already after a meditation session of only 20 minutes, first neurological changes could be observed. In another study, however, six to eleven hours were needed for this. For demonstrably more substantia grisea, on the other hand, perseverance is probably necessary: people who practice yoga intensively regularly for several years to decades sometimes have a larger volume of gray matter than those who have only been doing yoga for a short time. However, the cause-effect relationship in such studies is difficult: "It is also possible that the long-term yogis already had a larger brain volume before they started practicing," Cramer points out.

Is yoga safe?

Nearly 80 case reports are known in the medical literature about so-called "adverse events" associated with yoga. These range from muscle strains and injuries to torn ligaments and fractures to a worrisome increase in eye pressure. "Evidence of such risks is important," says health scientist Holger Cramer. However, such individual cases cannot be generalized.

In fact, injuries probably do not occur significantly more often in yoga than in other sports. This is shown by a comprehensive meta-analysis from 2015, in which Cramer participated. Only two percent of the study participants reported undesirable side effects from yoga practice; moreover, these usually passed quickly.

But beware: People with pre-existing conditions should definitely talk to the yoga teacher and, if necessary, to their doctor in advance.

"Lifestyle could also play a role," says neuroscientist Ott. Surveys show, for example, that compared to the population average, people who do yoga tend to be more physically active, generally eat a healthier diet, are less likely to be overweight, and are often well-educated - "all factors that have a positive effect on the structure and function of the brain," Ott explains. "Many studies also simply compare yoga practitioners to those who don't do yoga," adds psychologist Cramer. Such studies, he says, are significant in determining the absolute effects of yoga.

Additional studies with control groups doing a different sport would be important, as well as a comparison between the individual styles. Even though Hatha, Bikram, and Vinyasa are similar in their basic elements, they are different in their characteristics. Not to mention the usually small number of test subjects. On average, there are between 25 and 36 people - 100 if it comes up, but sometimes there are only four. "That's not representative," says Ott. Therefore, to distinguish the mechanisms of action more precisely, one needs data on lifestyle as well as long-term studies in addition to the MRI scans.

That yoga changes our brain and has a positive effect on the body and mind is nevertheless beyond question for numerous researchers. These are effects that, with a little luck, can also be used therapeutically. At the Charité, a team is currently investigating how well anxiety can be treated with yoga. To prevent dementia and treat stroke patients and people with Parkinson's disease, yoga may also be useful. "Exactly what the training should look like for these groups, however, needs to be studied," says neuroscientist Ott. Practicing yoga may be relaxing; exploring it, however, is still a lot of work.