In late 1971, Navy veteran Stephen Islas returned from Vietnam, but the war continued to rage in his head. "I came very close to committing suicide when I came home, I was that emotionally and mentally damaged," Islas remembers. At his college campus in Los Angeles, a friend suggested he check out a meditation class. He was skeptical, but he found that before long "there were moments that started shifting, where I was happy. I would experience these glimpses of calmness."
Forty-six years later, Islas says that he has never completely freed himself from his post-traumatic stress disorder, which was formally diagnosed in 2000 at the VA West Los Angeles Medical Center. But he's convinced that meditation has saved his life.
Various forms of meditation are now routinely offered to veterans with PTSD. It's also touted as a therapeutic tool to help anyone suffering from conditions and disorders including stress, anxiety, depression, addiction, and chronic pain. More broadly, meditation has come into vogue as a way to enhance human performance, finding its way into classrooms, businesses, sports locker rooms, and people's smartphones through internet apps like Headspace and Calm.
Mindfulness meditation has been used among U.S. veterans and active duty military to help those suffering from post-traumatic stress syndrome and to cope with the stress of deployment. Some work suggests that meditation can alter connectivity between regions of the brain in a way that can reduce stress. Here, U.S. soldiers meditate during a 15-minute mindfulness class in Baghdad in 2010. | (SPC. DANIEL SCHNEIDER/US ARMY/Courtesy Knowable)
"Mindfulness" meditation, a type of meditation that focuses the mind on the present moment, is wildly popular. It has become a billion-dollar business, according to the market research firm IBISWorld.
For all its popularity, however, it's still unclear exactly what mindfulness meditation does to the human brain, how it influences health, and to what extent it helps people suffering from physical and mental challenges. Meditation has been practiced for thousands of years, but psychologists and neuroscientists have studied it for only a few decades.
Some studies suggest that meditation can help people relax, manage chronic stress, and even reduce reliance on pain medication. Some of the most impressive studies to date involve a treatment called mindfulness-based cognitive therapy, which combines meditation with psychotherapy to help patients deal with thoughts that lead to depression. Randomized controlled trials have shown that the approach significantly reduces the risk of depression relapse in individuals who have previously had three or more major depressive episodes.
But many other studies on the effects of meditation have used only small numbers of subjects, lacked follow-up, and generally been less scientifically rigorous than other medical studies — clinical trials for new drugs, for example. A 2017 article in PTSD Research Quarterly that assessed evidence on meditation as a treatment for PTSD summed up the overall state of affairs: "This line of research is in its relative infancy."
While questions about the clinical outcomes of meditation persist, other studies have focused on a more fundamental issue: Does meditation physically change the brain? It's a tough question to answer, but as brain imaging techniques have advanced and meditation interventions have grown more popular, scientists have begun to take a systematic look at what's going on.
Meditation that requires one to sit still and focus on the mere act of breathing can encourage mindfulness, says psychologist David Creswell, who directs the Health and Human Performance Laboratory at Carnegie Mellon University in Pittsburgh. But most people spend most or all of their day being anything but mindful. They skip from one thought to another. They daydream. They ruminate about the past, and they worry about the future. They self-analyze and self-criticize.
In a 2010 study, Harvard researchers asked 2,250 adults about their thoughts and actions at random moments throughout their day via an iPhone app. People's minds wandered 47 percent of the time and mind wandering often triggered unhappiness, the scientists reported in Science.
"In contrast, the capacity to be mindful is associated with higher well-being in daily life," Creswell wrote in the 2017 Annual Review of Psychology. He cites a 2003 study by researchers at the University of Rochester showing a correlation between mindfulness and a number of indicators of well-being.
When people who meditate say they are paying attention to the present moment, they may be focused on their breathing, but maybe also on an emotion that surfaces and then passes, a mental image, inner chatter, or a sensation in the body. "Adopting an attitude of openness and acceptance toward one's experience is critical" to becoming more mindful, Creswell says. The idea is to view these moments with a detached and non-judgmental curiosity.
Creswell first became interested in mindfulness meditation when he took courses on psychology and Buddhism in high school. Later, in graduate school, he began studying meditation in connection with reducing stress and improving overall health.
"As a scientist, I'm never convinced. I've been trained to be skeptical," Creswell says. "Nonetheless, I do think that there were a number of experiences I had while on meditation retreats that really struck me as very foundational."
Mindfulness mediation, which aims to focus the mind on the present moment, is being tapped to treat stress, anxiety, depression, chronic pain, addiction and other conditions. But getting clear evidence of its utility for these conditions has been challenging, and even advocates say that more research is needed. Here, Barry Kerzin, an American physician and Buddhist monk, undergoes an electroencephalography, or EEG, test while meditating to measure electrical activity in his brain. | (ANTOINE LUTZ/WIKIMEDIA COMMONS/Courtesy Knowable)
Even the simple but challenging act of sitting still for an hour while meditating made a great impact on Creswell. "Having this disconnect between my body feeling in pain but my mind being completely silent and open … these were very powerful insights for me about how a [meditation] practice could really change people's lives, or fundamentally change how they relate to suffering in their lives," he says. "There wasn't a bolt-of-lightning moment for me, but a lot of these moments of insight in my own retreat experiences that suggested to me that it was worth spending time and effort to do the science."
People from different religious, cultural, and philosophical backgrounds have expounded the benefits of meditation for millennia. Meditation is perhaps most commonly associated with Buddhism, which views it as an instrument for achieving spiritual fulfillment and peace. Creswell calls the act of meditation "a basic feature of being human."
But the scientific evidence for its benefits is still lacking. "There is a common misperception in public and government domains that compelling clinical evidence exists for the broad and strong efficacy of mindfulness as a therapeutic intervention," an interdisciplinary group of 15 scholars write in an article entitled "Mind the Hype" in the January 2018 Perspectives on Psychological Science. The reality is that mindfulness-based therapies have shown "a mixture of only moderate, low, or no efficacy, depending on the disorder being treated," the scholars write, citing a 2014 meta-analysis commissioned by the U.S. Agency for Healthcare Research and Quality.
Much more research is needed before scientists can say what mental and physical disorders, in which individuals, can be effectively treated with mindfulness meditation, they conclude.
From the yoga mat to the lab
Alongside clinical work, neuroscientists have wanted to know how, if at all, meditation might change what actually happens inside the brain. Does meditation make certain regions more active than others, or more robustly connect one region to another? Does meditation result in new neurons, actually changing brain structure? Some studies suggest the answer is yes.
Neuroscientists have studied the physical effects of mindfulness meditation using functional magnetic resonance imaging (fMRI) and other techniques for the last two decades. Progress has followed on the growing recognition that the human brain is capable of physical changes throughout adulthood, even into old age — forming new connections and growing new neurons when someone learns a new skill, challenges themselves mentally or even just exercises. The emerging view of a brain that can be continually shaped through experience, dubbed neuroplasticity, replaced the long-held idea that after the first few decades of life, the brain's physiological trajectory was basically one of decline. A number of brain studies suggest that mindfulness meditation may spark neuroplastic renovations in the brain's function and structure.
Looking under the hood with fMRI, scientists have found that mindfulness meditation activates a network of brain regions that includes the insula (associated with compassion, empathy, and self-awareness), the putamen (learning), and portions of the anterior cingulate cortex (regulating blood pressure, heart rate, and other autonomic functions), and the prefrontal cortex (the hub of higher-order thinking skills such as planning, decision-making, and moderating social behavior). It's uncertain, however, whether these changes in brain activity can be sustained when the individual is not actively meditating, and if so how much people need to meditate for that to happen.
When it comes to actual structural changes in the brain, some studies suggest that mindfulness meditation may increase gray matter density in the hippocampus, a brain region essential to memory. Researchers including Britta Hölzel, now at the Technical University of Munich, and Sara Lazar of Massachusetts General Hospital found evidence for this in a 2011 study.
Some brain scan studies suggest that meditation alters not only brain activity but also brain structure. A 2014 review of published studies of both long-term and novice meditators highlighted nine brain structures (shown) that appear changed by meditation. Among them were the insula, involved in regulating feelings and emotions, and the hippocampus, essential for memory, as well as a number of gray matter regions (blue) and white matter pathways (red). | (K.C.R. FOX ET AL / NEUROSCIENCE AND BIOBEHAVIORAL REVIEWS 2014)
Though intriguing, these studies are nowhere near the end goal. "We need to understand the benefits that the changes in the brain have on behavior and well-being," Hölzel says. "'Changing the brain' sounds very impressive, but we don't understand what it actually means."
Lazar agrees. "Most of the data has only looked at changes over the course of two months of [meditation] practice … Most people feel that [meditation] continues to change and get deeper with extended practice. So we need to conduct studies that follow people for much longer time points."
Based on their studies of people engaged in meditation, Creswell and his colleagues have proposed that mindfulness acts as a buffer specifically against stress. It does this by increasing activity in regions of the prefrontal cortex that are important for "top-down stress regulation," while reducing activity and functional connectivity in regions associated with the brain's fight-or-flight stress response — in particular the amygdala.
The idea that mindfulness meditation engages parts of the brain involved in top-down stress regulation is widely accepted among researchers, says University of Michigan clinical psychologist Anthony King. But what's happening in relation to the amygdala is less clear, he says. The amygdala, one of the most primitive parts of the brain, is not just a simple alarm center associated with responding to threats. It's central to what's called the salience network, which is vital for noticing all kinds of important things in one's environment. In a mother, for example, the amygdala may become very active in response to her baby's joyful face.
Mindfulness meditation "helps people have what the old school psychotherapists call 'reflective capacity,'" King says. "Instead of automatically responding in certain ways, it allows people to have more nuance in their ability to respond to any type of situation — stressful, fearful, or otherwise — and create some psychological distance."
Two studies by Creswell and his colleagues, one in 2015 and the other in 2016, offer some initial findings that seem to support their view of mindfulness meditation as a buffer against stress. Both studies focused on the physiological effects of mindfulness mediation training on small groups of unemployed adults experiencing stress.
In the 2015 study, published in Social Cognitive and Affective Neuroscience, the researchers found that three days of intensive mindfulness meditation training reduced functional connectivity between the right amygdala, associated with the fight-or-flight stress response, and the subgenual anterior cingulate cortex, which plays a role in modulating emotions.
In the 2016 study, published in Biological Psychiatry, the researchers found that three days of intensive mindfulness meditation training led to increased connectivity between the default mode network, a network of regions engaged when the brain is at rest, and parts of the prefrontal cortex involved in regulating stress. The study also found that meditation led to reduced levels of interleukin-6, a biomarker in the blood for systemic inflammation that's elevated in high-stress populations.
Focus on PTSD, anxiety, and pain
King and his colleagues showed similarly promising results in 23 combat veterans of Afghanistan and Iraq with post-traumatic stress disorder in 2016 in Depression and Anxiety. Brain scans before and after mindfulness-based group therapy revealed an increase in resting-state connectivity between a network in the brain that allows people to control their attention and other parts of the brain involved in rumination and spontaneous thought. This particular connectivity has been seen in healthy people, as well as people who have meditated for long periods, says King.
"What's important about our study … is that people with PTSD can also have this change in brain connectivity patterns when they do mindfulness practice," King says. The more this connectivity increases as a result of mindfulness training, "the more their symptoms improve," he adds, summarizing a key finding of the study.
Studies of other conditions suggest similar improvements, although many involve small numbers of subjects and other limitations that make them far from conclusive. Nevertheless, mindfulness meditation may alleviate symptoms of general anxiety disorder, by increasing connectivity between the amygdala and the prefrontal cortex, thereby increasing a patient's ability to regulate emotions. Meditation may also lessen the perception of pain by reducing pain-related activation of the somatosensory cortex and increasing activation of areas involved in the cognitive regulation of pain.
Fundamentally, mindfulness is an elusive quality to study. It's an internally generated experience, not a drug that scientists can give to a patient. That creates a question when comparing mindfulness between individuals and especially between distinct studies. What's more, there is no universally accepted definition of mindfulness or agreement among researchers on the details of what it entails, Lazar and her colleagues note in the Perspectives on Psychological Science article.
In the context of PTSD, King says it's likely that mindfulness meditation will continue to supplement more conventional psychiatric treatments. "I would never recommend for people to go to a mindfulness class at the YMCA or the local health center and think that that's going to be the same as psychotherapy, because it is not. It really is not," King says. But "I think mindfulness is a useful technique in the context of therapy with somebody who's trained in PTSD treatment."
But people like Islas who have faced serious mental illness, and others who use mindfulness meditation to ease daily stress, say they're convinced the practice improves their lives. One day, scientists hope to be able to link that experience to what's physically happening in the meditating mind.