Meditation

Try a small experiment. Set a timer for thirty seconds and keep your attention on the sensation of breathing — nothing else, no commentary. Most people find that before the timer ends a thought has slipped in: a task for later, a memory, a remark about how well the exercise is going. Often the thought is not even noticed as a thought. It simply feels like you, thinking.

That small failure is the starting point of meditation. Contemplative traditions noticed thousands of years ago that the mind drifts constantly, and that much of what we call stress is carried by the drift. Modern psychology arrived at a similar observation by a different route. In a large experience-sampling study, people reported that their minds were wandering in close to half of the moments they were sampled, and they reported feeling less happy during those moments than when their attention was on what they were doing. ^[1] The study was correlational — it does not prove that wandering causes unhappiness — but it gave a measurable shape to an old intuition.

Meditation is, at its core, a set of techniques for working with that drift. Its traditions disagree about the ultimate goal, while modern research asks a narrower question: what changes can the practice reliably produce?

Training the Return

Meditation is often imagined as emptying the mind. Practitioners and researchers mostly describe something different: learning to notice what the mind is doing, and changing one's relationship to it.

Consider the breathing exercise again. When attention drifts, there is a moment — sometimes seconds later, sometimes minutes — when you realise you have drifted. You then bring attention back. In most forms of practice, that moment of noticing and returning is not a failure of meditation. It is the exercise, in the same way that the lift is the exercise in weight training.

Researchers have grouped the many traditional practices into a few families. ^[2,3,24]

• Focused attention. Attention is placed on a single object — the breath, a sound, a word repeated silently — and returned to it whenever it wanders. This trains the ability to sustain attention, detect distraction, and disengage from it.
• Open monitoring. There is no single object. The practitioner rests in awareness of whatever arises — sounds, bodily sensations, thoughts, emotions — without holding on to the pleasant or pushing away the unpleasant. The skill being trained is non-reactive awareness of experience as it unfolds.
• Loving-kindness and compassion. The practitioner deliberately cultivates warmth, typically by repeating phrases of goodwill directed first at oneself or a loved one and gradually extended to strangers and difficult people. ^[4] Here the aim is not only to observe mental states but to shape them.

A later framework groups practices by what they target: attentional practices (training attention), constructive practices (cultivating qualities such as compassion), and deconstructive practices (investigating the nature of experience itself, including the sense of self). ^[3] "Mindfulness" in modern usage usually refers to a mix of focused attention and open monitoring.

Where It Came From

Meditative practices appear in several ancient South Asian traditions. Techniques of concentration and absorption are described in early Hindu and yogic literature, and the Buddhist tradition developed a detailed vocabulary for attention and awareness: sati (usually translated as mindfulness), samatha (calm, concentration), vipassanā (insight), and mettā (loving-kindness). These practices spread and diversified as Buddhism moved through East Asia and Tibet, producing Chan and Zen sitting practice, Tibetan contemplative systems, and many others. Dating the earliest sources precisely is difficult, because many texts were transmitted orally for generations before being written down.

The modern scientific story begins much later. In 1979, the molecular biologist Jon Kabat-Zinn founded a clinic at the University of Massachusetts Medical School offering an eight-week course for patients with chronic pain and other conditions that conventional treatment had not resolved. He deliberately removed Buddhist terminology and presented the practices in secular, clinical language. ^[5,6] The course became Mindfulness-Based Stress Reduction (MBSR). About two decades later, a group of psychologists combined MBSR with elements of cognitive therapy to create Mindfulness-Based Cognitive Therapy (MBCT), designed specifically to prevent relapse in people who had recovered from recurrent depression. ^[7]

This secularisation made research possible, but it also changed the practice. Scholars of Buddhism have pointed out that the modern clinical idea of mindfulness — "non-judgmental awareness of the present moment" — is a specific, recent interpretation, not a neutral translation of what the ancient texts describe. ^[8] Traditional contexts embedded meditation in ethics, community, and long-term training; an eight-week course or a phone app is a very different thing. That difference matters when interpreting studies.

How It Seems to Work

A Cycle of Attention

When researchers asked meditators to press a button the moment they noticed their mind had wandered during breath-focused meditation, they could reconstruct a repeating cycle from brain imaging. ^[9]

1. Mind wandering — attention drifts into thought.
2. Awareness — the drift is noticed.
3. Shifting — attention is deliberately redirected.
4. Sustained focus — attention stays with the breath, until the next drift.

Each phase was associated with activity in a different large-scale brain network. Mind wandering coincided with the default mode network — a set of regions, including the medial prefrontal cortex and posterior cingulate cortex, that are active during self-referential thought, daydreaming, and thinking about the past and future. Noticing the drift coincided with the salience network, which flags events that deserve attention. Redirecting and holding attention involved executive control regions in the lateral prefrontal and parietal cortex. ^[9]

This gives a plausible mechanical picture of practice: repeated cycles train the transition from being lost in thought to noticing it. In a study comparing experienced meditators with beginners, the main hubs of the default mode network were relatively less active in the experienced group during several kinds of meditation, and were more strongly coupled to regions involved in monitoring and control. ^[10] The sample was small — about a dozen people per group — and cross-sectional, so it shows an association with long-term practice rather than a change caused by it.

Three Components

A widely cited review organised the proposed mechanisms of mindfulness meditation into three interacting components. ^[2]

• Attention control — sustaining attention and disengaging from distractors.
• Emotion regulation — changing how strongly one reacts to emotional events, and how quickly one recovers.
• Altered self-awareness — a shift in how one relates to thoughts, sensations, and the narrative sense of "me".

A simple scenario shows how these link. Someone says something that makes you angry. Without noticing, you begin rehearsing the argument: what they said, why you are right, what you will say next. The rehearsal keeps the physiology of anger running. The claim of mindfulness training is not that anger will not arise, but that you are more likely to notice the rehearsal as rehearsal — and with that noticing comes a choice about whether to continue it. Clinical researchers call this shift decentering: relating to thoughts as passing mental events rather than as facts or commands. ^[7] It is thought to be a central ingredient of MBCT's effect on depressive relapse, where ruminative thought patterns can pull a recovered person back into an episode.

Interoception

Many practices direct attention to bodily sensations: breath, heartbeat, tension, warmth. The ability to perceive the internal state of the body is called interoception. Researchers have proposed that meditation trains more accurate and less reactive interoceptive awareness, and that this may help with stress, pain, and emotional regulation, since emotions are partly built from bodily signals. ^[11] This is an active research area. The theory is coherent, but the evidence that meditation reliably improves objective interoceptive accuracy is mixed.

The Question of the Self

Some teachers argue that the deepest purpose of meditation is not stress reduction at all. In the conversation that inspired this article, the neuroscientist and meditation teacher Sam Harris describes the ordinary feeling of being a thinker "behind the eyes", separate from one's experience, and argues that careful attention reveals no such separate subject — only experience itself. ^[12] He frames the benefits of calm and focus as secondary to that recognition.

It is important to be precise about what kind of claim this is.

• Established: people who meditate report changes in how they experience the sense of self, and deconstructive practices explicitly aim to produce such changes. ^[3]
• Accepted theory, still developing: the default mode network is associated with self-referential thinking, and experienced meditators show differences in its activity. ^[10]
• Philosophical interpretation: the statement that the self "is an illusion" is a claim about the nature of subjective experience. It is reported by many contemplatives and debated by philosophers. No brain scan can confirm it, because the claim is about what experience is like from the inside, not about which region lights up.

The idea connects to older debates about agency and control; see Determinism and Taoism, whose tradition of wu wei describes a similar dissolving of effortful selfhood.

The Evidence

Measuring the Size of an Effect

Before looking at results, it helps to know how they are usually reported. Trials often compare an intervention group with a control group on a questionnaire score, such as anxiety. Because different questionnaires use different scales, results are converted into a standardised mean difference:

Here $\bar{x}_{\text{treatment}}$ and $\bar{x}_{\text{control}}$ are the average scores in the two groups, and $s_{\text{pooled}}$ is the typical spread (standard deviation) of scores within the groups. A value of $d = 0.2$ is conventionally called small, $0.5$ moderate, and $0.8$ large. In plain terms, $d = 0.3$ means the average person in the meditation group ended up about a third of a standard deviation better off than the average person in the control group — noticeable, but far from transformative.

Stress, Anxiety, and Depression

The most frequently cited summary is a 2014 systematic review and meta-analysis for the US Agency for Healthcare Research and Quality, published in JAMA Internal Medicine. It screened more than 18,000 citations and included 47 randomised trials with about 3,500 participants. ^[13] Compared with non-specific active controls, mindfulness programmes produced moderate-strength evidence of improvement in anxiety ($d \approx 0.38$ at eight weeks), depression ($d \approx 0.30$), and pain ($d \approx 0.33$). Evidence for effects on stress and quality of life was weaker. Crucially, the review found no evidence that meditation was better than other active treatments such as exercise, relaxation, cognitive behavioural therapy, or medication.

This is the most honest one-sentence summary of the field: meditation programmes produce small to moderate benefits for anxiety, depression, and pain, roughly comparable to other reasonable interventions, not superior to them.

Later work has broadly confirmed that picture. An individual-participant-data meta-analysis of 13 trials with more than 2,300 adults in non-clinical settings found that teacher-led, group-based mindfulness programmes reduced psychological distress compared with passive controls, with a small-to-moderate effect ($d \approx 0.32$). ^[14] The authors stressed that this applies to volunteers attending in-person programmes, not necessarily to self-guided apps or compulsory workplace schemes.

A notable 2023 randomised trial compared MBSR directly with escitalopram, a first-line antidepressant used for anxiety disorders. In about 200 adults who completed the trial, MBSR was statistically non-inferior to the medication over eight weeks. ^[15] This is one trial and needs replication, but it is an unusually direct comparison with an established treatment.

Preventing Depressive Relapse

MBCT has one of the stronger evidence bases in the field. It was designed for people who have recovered from several episodes of depression and remain at high risk of relapse. An individual-patient-data meta-analysis of nine randomised trials, including 1,258 patients, found that MBCT reduced the risk of relapse over 60 weeks compared with those not receiving it, with a hazard ratio of 0.69. ^[16]

A hazard ratio compares the rate at which an event (here, relapse) occurs in one group relative to another over time:

where $h(t)$ is the instantaneous risk of relapse at time $t$ among people who have not yet relapsed. A value of 0.69 means relapse occurred at roughly 69% of the control rate — about a 31% relative reduction. In the subset of comparisons against active treatments, mostly maintenance antidepressant medication, MBCT still showed a lower relapse risk (hazard ratio 0.79), and people with more residual depressive symptoms at the start appeared to benefit most. ^[16] This is one of the reasons MBCT has entered clinical guidelines for recurrent depression, such as those of the UK's National Institute for Health and Care Excellence.

Changes in the Brain

Popular articles frequently claim that meditation "rewires" or "grows" the brain. The evidence here is more fragile than the clinical evidence.

Early studies generated much excitement. One widely reported study found increases in grey matter density in regions including the hippocampus after an eight-week MBSR course, compared with a waitlist group. ^[17] A 2014 meta-analysis of 21 morphometric studies reported moderate differences in several regions between meditators and non-meditators, while warning about small samples, cross-sectional designs, and likely publication bias. ^[18]

Then a larger, more rigorous test was run. Researchers combined two randomised trials with 218 meditation-naïve participants, assigned to MBSR, a well-matched active health programme, or a waitlist, and scanned them before and after. They found no evidence that MBSR changed grey matter volume, grey matter density, or cortical thickness compared with either control group. ^[19] The authors — from a centre that has long championed meditation research — noted that the earlier structural findings had been widely cited despite major methodological limitations, and that their larger, actively controlled study failed to replicate them.

This does not show that long-term practice over years has no structural effect; that remains an open question. It does show that the familiar headline, "eight weeks of mindfulness changes the shape of your brain", is not supported by the best available test.

Limitations and Open Problems

In 2018, fifteen researchers — many of them meditation scientists themselves — published a critique titled "Mind the Hype". ^[20] Their central concerns remain relevant.

• Definition. "Mindfulness" is used to mean a personality trait, a state, a set of practices, a clinical programme, and a Buddhist concept. Studies measuring different things under the same name are hard to compare.
• Controls. Many trials compare meditation with a waitlist. People who receive any engaging, structured programme tend to feel better, partly through expectation, attention from instructors, and social contact (see Placebo). When meditation is compared with well-designed active controls, effects typically shrink. ^[13,19]
• Measurement. Most outcomes are self-reported questionnaires, which are sensitive to participants' expectations and to their wish to please researchers. Participants in a meditation trial usually know they are meditating; blinding is nearly impossible.
• Sample size and bias. Many studies, especially neuroimaging studies, are small. Small studies with positive results are more likely to be published than small studies with null results, which inflates the apparent effect across the literature. ^[18,20]
• Adverse effects. Meditation is often presented as risk-free. It is not.

Adverse Effects

A mixed-methods study interviewed 60 Western Buddhist practitioners and 32 teachers about challenging meditation experiences. It catalogued 59 categories of difficult effects — including anxiety, panic, perceptual changes, re-experiencing of trauma, and disturbing changes in the sense of self — some lasting months to years. ^[21] Because participants were deliberately recruited for having had difficult experiences, the study describes what can happen, not how often it happens.

For frequency, a 2020 systematic review of 83 studies with about 6,700 participants estimated that roughly 8% of participants experienced some adverse event, most commonly anxiety and depression. ^[22] Rates were much lower in experimental trials than in observational studies, and many trials never asked about harms in the first place. The honest conclusion is that most people who meditate experience no serious harm, a minority experience significant difficulty, and the risks are higher with intensive practice, such as long silent retreats, and in people with a history of trauma or psychosis.

What Remains Unknown

• Which components of a programme — the meditation itself, the group, the teacher, the expectation of benefit — account for the effect.
• Whether benefits persist when people stop practising, and how much practice is needed.
• Whether self-guided apps produce effects comparable to teacher-led programmes.
• Whether long-term, intensive practice produces durable changes in brain structure, as opposed to the functional changes that appear during practice.
• Who is most likely to benefit, and who is most likely to be harmed. ^[14,23]

Summary of Certainty

• Established fact: mind wandering is frequent; meditation trials show small to moderate improvements in anxiety, depression, and pain compared with passive or non-specific controls. ^[1,13,14]
• Well-supported: MBCT reduces the risk of depressive relapse in people with recurrent depression. ^[16]
• Accepted theory, still developing: meditation works through attention control, emotion regulation, and altered self-awareness, with measurable differences in activity of the default mode, salience, and executive networks. ^[2,9,10]
• Weaker than popularly stated: claims that short programmes change brain structure. ^[19]
• Philosophical interpretation: claims that meditation reveals the self to be an illusion. ^[3,12]

What the Evidence Leaves Us

Meditation is one of the oldest deliberate technologies for changing the mind, and one of the few that anyone can practise with no equipment. Science has taken it seriously for nearly half a century, and the results are neither the miracle promised by enthusiasts nor the nothing claimed by sceptics. For many people, it offers a modest, real, low-cost benefit, comparable to other good options, and for people with recurrent depression it provides a genuinely useful clinical tool.

Its scientific story is also a lesson in how evidence matures. An exciting early finding, a wave of small studies, a critical correction, and then larger and more careful trials that settle on a smaller but more trustworthy effect: that pattern is typical of new fields, and meditation research has lived through it in public.

What remains open is the question the traditions considered most important: what attention, emotion, and the sense of self actually are, and how much they can be changed by training. That question sits at the boundary of neuroscience, psychology, and philosophy, and it connects meditation to much older reflections on the causes of suffering. The tools are ancient; the measurements are new; the answer is not yet complete.

References

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[2] Tang, Y.-Y., Hölzel, B. K., & Posner, M. I. (2015). "The neuroscience of mindfulness meditation." Nature Reviews Neuroscience, 16(4), 213–225. https://doi.org/10.1038/nrn3916

[3] Dahl, C. J., Lutz, A., & Davidson, R. J. (2015). "Reconstructing and deconstructing the self: cognitive mechanisms in meditation practice." Trends in Cognitive Sciences, 19(9), 515–523. https://doi.org/10.1016/j.tics.2015.07.001

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[12] Huberman Lab (n.d.). "Essentials: Using Meditation to Focus, View Consciousness & Expand Your Mind | Dr. Sam Harris." YouTube (further watching). https://www.youtube.com/watch?v=LQI8tl8S2PE

[13] Goyal, M., Singh, S., Sibinga, E. M. S., et al. (2014). "Meditation Programs for Psychological Stress and Well-being: A Systematic Review and Meta-analysis." JAMA Internal Medicine, 174(3), 357–368. https://doi.org/10.1001/jamainternmed.2013.13018

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[21] Lindahl, J. R., Fisher, N. E., Cooper, D. J., Rosen, R. K., & Britton, W. B. (2017). "The varieties of contemplative experience: A mixed-methods study of meditation-related challenges in Western Buddhists." PLOS ONE, 12(5), e0176239. https://doi.org/10.1371/journal.pone.0176239

[22] Farias, M., Maraldi, E., Wallenkampf, K. C., & Lucchetti, G. (2020). "Adverse events in meditation practices and meditation-based therapies: a systematic review." Acta Psychiatrica Scandinavica, 142(5), 374–393. https://doi.org/10.1111/acps.13225

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[24] Lutz, A., Slagter, H. A., Dunne, J. D., & Davidson, R. J. (2008). "Attention regulation and monitoring in meditation." Trends in Cognitive Sciences, 12(4), 163–169. https://doi.org/10.1016/j.tics.2008.01.005