Research on contemplative practice moves quickly, and most of it reaches the public as headlines. Here are six studies from the last few years that are worth knowing about, including two that disappoint. For each: what the researchers did, what they found, and how far the finding goes.
Breathing
Five minutes of long exhales, every day for a month
A remote randomised trial gave 108 people one of four five-minute daily practices for a month: cyclic sighing (two inhales through the nose, then a long, slow exhale), box breathing (equal counts in, hold, out), cyclic hyperventilation with retention, or mindfulness meditation.
Every group improved: more positive mood, less anxiety, less negative mood. Cyclic sighing produced the largest rise in positive mood and the mindfulness group the smallest, and the breathing practices, cyclic sighing especially, lowered breathing rate more than meditation did.
How far it goes: the groups were small (21 to 33 people each), people practised at home, and mood was self-reported. It is a promising result for a very cheap practice, not a final verdict on meditation.
Balban MY et al. Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine, 2023. PMID 36630953
What the breathwork trials add up to
A meta-analysis pooled randomised controlled trials of breathwork in adults — 785 participants in all. Compared with control groups, breathwork was linked to lower stress (12 trials), lower anxiety (20 trials) and lower depressive symptoms (18 trials).
The effects were small to medium: effect sizes of about 0.35 for stress, 0.32 for anxiety and 0.40 for depression.
How far it goes: many of the trials carried a moderate risk of bias, and few followed people up for long. Breathwork helps, modestly, in the short term. Anyone promising more is ahead of the evidence.
Fincham GW, Strauss C, Montero-Marin J, Cavanagh K. Effect of breathwork on stress and mental health: a meta-analysis of randomised-controlled trials. Scientific Reports 13:432, 2023. doi:10.1038/s41598-022-27247-y
Slow breathing and the heart
A systematic review gathered 223 studies of voluntary slow breathing. Across them, slowing the breath raised vagally-mediated heart rate variability, a marker of the calming branch of the nervous system. The rise showed up during the breathing itself, straight after a single session, and after courses of several sessions.
How far it goes: heart rate variability is a marker, not a feeling or a diagnosis. But it is the physiological reason slow breathing — around six breaths a minute, with a longer out-breath — keeps turning up as one of the best-supported practices there is.
Laborde S et al. Effects of voluntary slow breathing on heart rate and heart rate variability: a systematic review and a meta-analysis. Neuroscience & Biobehavioral Reviews 138:104711, 2022. doi:10.1016/j.neubiorev.2022.104711
Yoga
Yoga for depressive symptoms, in people already unwell
This review looked only at people with a diagnosed mental disorder: 13 randomised trials and 632 participants. Physically active yoga reduced depressive symptoms by a moderate amount compared with waiting lists, usual care or attention-matched activities, and people who did more sessions a week saw larger reductions.
How far it goes: thirteen trials is a small base. It supports yoga as a useful addition to care, not a replacement for it.
Brinsley J et al. Effects of yoga on depressive symptoms in people with mental disorders: a systematic review and meta-analysis. British Journal of Sports Medicine, 2021. doi:10.1136/bjsports-2019-101242
Meditation
Eight weeks of mindfulness did not change brain structure
You may have read that a mindfulness course grows grey matter. Two combined randomised trials tested this with 218 people new to meditation, scanned before and after: 75 did an eight-week mindfulness-based stress reduction course, 73 an active control programme, and 70 waited.
They found no evidence that the course changed grey matter volume, grey matter density or cortical thickness. The authors point out that the earlier, widely quoted studies had major methodological limitations.
How far it goes: this is about brain structure after eight weeks, not about whether mindfulness helps people. It is a good example of a popular claim meeting a larger, better-designed test — and the kind of result this magazine will always report.
Kral TRA et al. Absence of structural brain changes from mindfulness-based stress reduction: two combined randomized controlled trials. Science Advances 8(20):eabk3316, 2022. doi:10.1126/sciadv.abk3316
The nasal cycle
The open nostril doesn't set the brain's side
Swara teaching often links the open nostril to one side of the brain. This study measured the nasal cycle in 35 people with a portable airflow meter and compared it with scans of the olfactory bulbs and brain responses to smells.
The nasal cycle was independent of the size of the olfactory bulbs, and brain activity during smelling did not follow which nostril was dominant.
How far it goes: a small study, about smell rather than thinking. But it is one more measurement that fails to find the tidy left-right brain link the tradition assumes — the same pattern we describe in our piece on Nadi Shodhana.
Thaploo D, Joshi A, Thomas M, Hummel T. Lateralisation of nasal cycle is not reflected in the olfactory bulb volumes and cerebral activations. European Journal of Neuroscience, 2024. Publication record
The thread through all six
The breathing studies agree with each other and with what the old texts got right: slowing the breath, especially the out-breath, calms the body in ways that can be measured. The brain-change and left-right claims are where popular accounts run ahead of the data. None of that makes practice less worth doing. It means we can say more precisely why.