The biggest meditation trials found no memory boost or brain growth

The headline usually runs something like this: eight weeks of meditation grows your brain. It has circulated in popular media for more than a decade, and it sounds like the rare self-improvement promise with a brain scan behind it.

The best-known scan behind it came from 16 meditators and 17 people on a waiting list. In 2022, researchers at the University of Wisconsin-Madison ran the test again with 218 people, checked the exact brain regions the original team had flagged, and found no structural change that set the meditators apart.

That pattern runs through this whole subject. Small studies, and studies comparing longtime meditators with people who never meditated, produced striking pictures. Larger randomized trials, where chance decides who meditates and who doesn’t, mostly found nothing on brain structure or on memory and thinking tests. They also turned up a detail that explains much of the early excitement: in one 18-month trial, the group that did nothing at all improved on attention tests as much as either class did.

This article covers what meditation has and hasn’t been shown to do for memory, attention and the physical brain. What it does for stress, sleep and mood is a different question with different evidence, taken up in the library’s other meditation pieces.

Where the brain-growth idea came from

Two early studies from Massachusetts General Hospital show how the idea took shape. In 2005, a team led by Sara W. Lazar scanned 20 people with long experience in Insight meditation, a practice built on close attention to inner experience, and compared them with matched non-meditators. Parts of the prefrontal cortex and the right anterior insula, regions tied to attention and body awareness, were thicker in the meditators, and the prefrontal difference was largest in the older participants.

That design has a built-in weakness. It compares people who chose to meditate for years with people who didn’t, so any difference could come from the practice or from whatever leads a person to take it up and stay with it.

A 2011 study led by Britta K. Hölzel tried to get around that. It scanned 16 newcomers before and after an 8-week course in mindfulness-based stress reduction (MBSR, a widely taught program of meditation, gentle yoga and body awareness) and compared them with 17 people on a waiting list. The team reported increases in gray matter concentration in the left hippocampus, a hub for memory, and in several other regions. The Wisconsin team later wrote that a few small studies like this one had carried the idea of a brain-changing 8-week course into popular media.

By 2014, a review in Neuroscience and Biobehavioral Reviews could pool 21 imaging studies covering about 300 practitioners. It found eight regions that consistently differed in meditators, with a medium-sized overall effect. In the same summary, the authors flagged two serious problems: positive results were likelier to reach print, and many of the studies had weak methods.

The large replication that found nothing

The Wisconsin study, published in Science Advances, combined two randomized trials of healthy adults aged 18 to 65 who had never meditated. Of the 218 who completed scans before and after, 75 took MBSR, 73 took a matched course of exercise, music therapy and nutrition education, and 70 waited.

Brain structure changed no more after MBSR than after either comparison. That held for gray matter volume, gray matter density and cortical thickness, across the whole brain and inside the regions from earlier MBSR studies, including outlines supplied by the Hölzel team. The authors summed it up in one line: “This study found no evidence that 2 months of training in mindfulness meditation among novices produced neurostructural changes.”

Participants weren’t slacking. They logged an average of 32 hours of home practice, compared with 23 hours in the earlier work. Self-reported mindfulness rose after MBSR, but it rose about as much after the exercise-and-nutrition course, which suggests the questionnaire was picking up something general about taking a wellness class.

The authors also explained why the early findings may have looked so strong. Those studies had 20 or fewer people per group, small enough that the authors suspected inflated effects, and together had been cited more than 3,200 times.

They were careful about limits, too. Their volunteers were unusually healthy, and the study recruited no one older than 65. They also pointed to a separate, well-powered study of training about 50 percent longer than MBSR that did report cortical thickening, which leaves open whether longer or more focused practice behaves differently.

Eighteen months of practice in older adults

Scans are one thing. What most people want to know is whether meditation keeps memory sharp with age. Two trials ran long enough to test that directly.

The US trial

MEDEX, published in JAMA in December 2022, enrolled 585 adults aged 65 to 84 at Washington University in St. Louis and the University of California, San Diego. All had noticed some change in their thinking, and none had dementia. For 18 months they were randomly assigned to MBSR with a goal of an hour of meditation a day, to exercise of at least 300 minutes a week, to both, or to health education classes.

At six months, the main checkpoint, mindfulness training had no effect on episodic memory, the memory for events and details, or on executive function, the planning and switching skills that run daily life. Nothing had changed by 18 months either, and MRI measures of the hippocampus and prefrontal cortex showed no gain. The investigators concluded: “The findings do not support the use of these interventions for improving cognition in older adults with subjective cognitive concerns.” The exercise arm’s matching null result sits alongside the other long trials in our coverage of exercise and thinking.

Washington University’s announcement added a telling detail: all four groups scored slightly better on retesting, which the investigators attributed to practice effects. First author Eric J. Lenze stressed that the team was not telling anyone to give up meditation or exercise, that the results apply to healthy older adults rather than people with dementia or depression, and that NIH had funded five more years of follow-up.

The French trial

Age-Well, run in Caen, France, randomly assigned 137 cognitively healthy adults 65 and older to 18 months of meditation training, to English lessons designed to match it hour for hour, or to no program. Both active groups met for two hours a week, practiced at home at least 20 minutes a day and attended day-long intensive sessions. All but one participant finished.

The main results, published in JAMA Neurology in 2022, showed no difference in volume change in the two target regions, the anterior cingulate cortex and the insula. Blood flow to those regions, the other main measure, edged toward the meditation group, but those differences did not reach statistical significance. Meditation did beat English lessons on a combined measure of attention regulation, social and emotional capacities, and self-knowledge.

The thinking-test results followed in 2023. Neither program improved a global memory-and-thinking score, episodic memory, executive function or attention compared with doing nothing. Attention scores rose in every group: by 0.29 standard deviations with meditation, 0.27 with English and 0.35 with no program at all. A standard deviation is the usual spread of scores from one person to the next, so these were modest gains. The people who changed nothing did at least as well as either class, and the differences between groups were not statistically significant. The authors judged that the improvements likely reflected expectancy or practice effects.

Meditators in Age-Well reported regulating their attention better. On the tests, their attention didn’t stand out from the other groups. Feeling sharper and testing sharper turned out to be different things.

People already worried about their memory

A third trial, SCD-Well, recruited 147 people with subjective cognitive decline, meaning they sensed their thinking had slipped though standard tests looked normal, from memory clinics in four European countries. An 8-week mindfulness course and an 8-week health self-management course produced nearly identical gains on a standardized global thinking score, 0.34 and 0.30 by the six-month check, months after the courses had ended. Both groups improved, and the researchers found no sign that retesting alone explained it. Nothing singled out meditation.

Why everyone’s scores rise

People do better the second time they see a test because the format is familiar and some items stick. They may also try harder when they expect a program to help. That is why the comparison group decides what a trial can claim. How retesting shapes scores gets a fuller explanation in the library’s guide to cognitive tests.

The decades-of-practice puzzle

A 2025 analysis in Scientific Reports by the Age-Well team complicates the picture. It compared 25 older expert meditators, each with more than 20 years of practice, with the 135 trial participants, using a machine-learning model that estimates a brain age from MRI and PET scans.

The experts’ brains looked younger for their age than those of the trial participants, and the gap tracked with how many hours they had meditated. Eighteen months of randomized training, however, had no significant effect on brain age.

There are two ways to read that. The authors read it as a sign that benefits need sustained practice over many years. The other reading is selection: the Wisconsin team noted that people who practice for decades may differ from non-meditators before they ever start, and may live differently in many ways. Both could be partly true, and no trial is likely to assign people to 20 years of practice. For now, the claim that meditation slows brain aging rests on comparisons, not experiments.

What pooled studies show

Combining many trials points to a small, specific effect rather than none at all.

A meta-analysis in Neuropsychology Review, published online in 2021 by a team based at University College London, pooled randomized studies of mindfulness programs in adults of all ages: 56 studies with 2,931 people, 45 of them combined statistically. The overall effect on thinking tests was small, about one-seventh of a standard deviation. By domain, only executive function and working memory, the mental scratchpad for holding information while you use it, beat comparison groups, and adults over 60 showed a significant effect. But mindfulness programs outperformed only inactive comparisons such as waiting lists, not active ones such as other classes, and most studies had an unclear risk of bias.

A 2025 review in Frontiers in Public Health narrowed the lens to 25 randomized trials in people with subjective decline, mild cognitive impairment or Alzheimer’s disease. On a 30-point screening test, reported by 14 of those trials, meditation groups gained about 2.2 points more than comparison groups. That sounds firmer than it is. The authors rated the certainty of the evidence low, results varied enormously from trial to trial, and meditation beat usual care and cognitive rehabilitation but not health education, aerobic exercise or tai chi. The trials also mixed very different practices, from MBSR to chanting meditation and Kundalini yoga.

The brain-imaging work in mild cognitive impairment is thinner still. A 2013 pilot study at Beth Israel Deaconess Medical Center in Boston randomized 14 adults and reported only trends toward less shrinkage of the hippocampus, with a call for larger and longer studies.

Where each claim stands

Graded with the library’s five evidence verdicts:

• Eight weeks of mindfulness grows gray matter. Tested and not supported, for standard courses in healthy adults. Longer or more focused training hasn’t been tested at the same scale.
• Meditation protects memory as you age. Tested and not supported in healthy or mildly worried older adults, over periods from 8 weeks to 18 months.
• Meditation sharpens working memory and related planning skills. Positive evidence, contested interpretation. Small pooled gains appear against waiting lists, not against other engaging activities.
• Meditation slows brain aging. Insufficient evidence. Longtime meditators look younger on scans in small comparisons, but the one randomized test, 18 months long, found no effect, and no trial has run for decades.
• Meditation improves thinking in mild cognitive impairment or Alzheimer’s disease. Insufficient evidence: low-certainty results from small, varied trials, with no advantage over active alternatives.

How to read the next meditation-and-brain headline

These questions sort strong claims from weak ones quickly.

1. Did chance decide who meditated? A comparison of longtime meditators with non-meditators can’t separate the practice from the person.
2. How many people were scanned? In this field, imaging studies with 20 or fewer per group have produced results that a much larger trial could not repeat.
3. What did the comparison group do? Beating a waiting list is far easier than beating a class that offers attention, company and hope.
4. Is the result a picture or a performance? A changed region on a scan isn’t a better memory. Look for something a person would notice in daily life.
5. Did every group improve? If the comparison group rose too, retesting is the likeliest explanation.
6. Who was studied? Findings in healthy 40-year-olds don’t automatically carry to 75-year-olds, or the reverse.

Harms are uncommon but real

The National Center for Complementary and Integrative Health, in its June 2022 overview, describes meditation as generally low-risk while noting that few studies have looked for harm. A 2020 review in Acta Psychiatrica Scandinavica of 83 studies with 6,703 meditators found adverse events in 8.3 percent of participants overall: 3.7 percent in experimental studies and 33.2 percent in observational ones. Anxiety, depression and unusual thinking experiences were the most common; suicidal behavior was among the least frequent. The reviewers noted that such events can occur in people with no history of mental health problems.

Asking people directly turns up more, because it counts milder and briefer experiences. A US population survey led by University of Wisconsin-Madison researchers and published in 2022 followed up 434 adults who had meditated. Half reported at least one specific adverse effect, about 1 in 10 described effects lasting a month or longer, and 1.2 percent reported impaired functioning for at least a month. Anxiety and re-experiencing of traumatic memories led the list, and childhood adversity was linked with higher risk. Those who reported adverse effects were as glad to have meditated as everyone else.

In a Brown University study of 96 people who completed 8-week mindfulness-based cognitive therapy, lasting bad effects affected 6 to 14 percent. They were tied to hyperarousal, feeling keyed up and unable to settle, and to dissociation, feeling detached from one’s body or surroundings. The authors put the overall rate of passing distress on par with other psychological treatments.

When a professional should weigh in

• A new or worsening memory problem calls for an evaluation, not a practice standing in for one. NCCIH advises against using meditation to replace conventional care or to postpone seeing a provider about a medical problem. The memory-evaluation article walks through what a workup involves.
• Anxiety, low mood, panic, flashbacks or a sense of detachment that begins or worsens with practice and doesn’t settle is worth raising with a mental health clinician, who can judge whether the practice, its intensity or something else is driving it.
• A history of trauma or childhood adversity deserves a conversation first. Childhood adversity was linked with higher risk in the US survey, and re-living traumatic memories was among the most common reactions. Whether an intensive course or silent retreat is a good fit is a question for a clinician who knows that history.
• Thoughts of suicide or self-harm need help now: call or text 988 to reach the 988 Suicide & Crisis Lifeline, and call 911 if someone is in immediate danger.

The takeaway

The best-controlled trials found no change in brain structure after an 8-week course, no memory benefit after 18 months, and test-score gains that matched those of people who took a different class or did nothing. The small edge on working memory in pooled studies is real enough to keep studying and too small to promise. People value meditation for many reasons, and none of this argues against them. It argues against selling meditation as a brain upgrade or a shield against dementia. When the next claim arrives with a brain image attached, the most useful question is what the comparison group did.

Sources

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