Om (also written as Aum) is a sacred syllable in yoga that represents the totality of existence, consciousness, and the self. It’s the sound you’ll hear chanted at the beginning or end of many yoga classes, often drawn out in a single long exhalation. While it might seem like a simple sound, Om carries thousands of years of philosophical meaning and, as modern research shows, produces measurable changes in the brain and nervous system.
The Three Sounds and What They Represent
Om is actually three distinct sounds blended together: A (pronounced “ah”), U (pronounced “oo”), and M (a humming sound with closed lips). Each sound maps to a state of consciousness described in the Mandukya Upanishad, one of the oldest philosophical texts in the yoga tradition.
- A (ah): the waking state, your everyday conscious awareness of the physical world
- U (oo): the dreaming state, the subtler layer of consciousness where the mind creates inner experiences
- M (mmm): deep, dreamless sleep, the subconscious state where awareness rests without content
Then there’s a fourth element: the silence after the sound fades. This silence represents what the tradition calls Turiya, a state of pure awareness that transcends the other three. It’s the moment when, according to the philosophy, the individual self recognizes its unity with everything else. So chanting Om is meant to be a miniature journey through all states of consciousness, ending in stillness.
The Written Symbol
The Om symbol (ॐ) is a character in Devanagari script that combines the letters for A and U with a nasal mark representing M. Its three curves are commonly interpreted as the three states of consciousness: waking, dreaming, and deep sleep. The dot above the symbol represents the fourth transcendent state, and the crescent beneath the dot symbolizes the veil between ordinary awareness and that deeper state. Some traditions read additional meaning into the curves, linking them to the three worlds (earth, atmosphere, and heaven) or three major Hindu deities.
How Om Affects the Brain
A functional MRI study published in the International Journal of Yoga scanned the brains of 12 volunteers while they chanted Om aloud. The results were striking: chanting produced significant deactivation in the amygdala (the brain’s threat-detection center), the hippocampus (involved in memory and emotional processing), the anterior cingulate cortex, and the thalamus. In plain terms, the parts of the brain responsible for stress, fear, and emotional reactivity quieted down. No areas of the brain showed increased activation during chanting.
The control condition was telling. When participants simply pronounced “ssss” instead of Om, none of these brain changes occurred. This suggests something specific about the sound of Om, not just the act of vocalizing, drives the calming effect.
Why the Vibration Matters
The humming “M” portion of Om creates a vibration you can feel in your throat, sinuses, and around your ears. Researchers believe these vibrations travel through branches of the vagus nerve, a major nerve that runs from the brainstem down through the neck and into the chest and abdomen. Stimulating vagal centers shifts the nervous system away from the “fight or flight” response and toward a “rest and digest” state. This is the same basic mechanism behind clinical vagus nerve stimulation devices used for conditions like epilepsy and depression, though Om chanting is obviously far less intense.
The shift shows up clearly in heart rate variability (HRV) measurements. In a randomized controlled trial of patients with high blood pressure, one month of Om chanting practice significantly increased parasympathetic activity. Key HRV markers improved both immediately after a single session and after four weeks of regular practice. Participants also showed reduced pulse rate and lower systolic and diastolic blood pressure.
Effects on Emotional Processing
A study published in Frontiers in Psychology measured brain electrical activity while participants either chanted Om or simply viewed negative and neutral images. When people chanted Om while looking at disturbing images, they rated those images as less unpleasant compared to viewing them in silence. The effect was specific to negative content. Neutral images weren’t rated differently between the two conditions.
Separately, a study of bus drivers found that chanting Om for 20 minutes a day, six days a week over four weeks significantly reduced anxiety scores compared to a control group that didn’t chant. Another study found that just 20 days of Om practice lowered resting heart rate and respiratory rate.
What Happens to Your Breathing
One of the most dramatic physiological effects of Om chanting is how drastically it slows breathing. Research published in Frontiers in Physiology found that during Om chanting, breathing rate dropped from an average of about 20 cycles per minute to roughly 3.5 cycles per minute. Each chant takes a full, slow exhalation, creating a breathing rhythm of approximately 0.05 Hz (one breath every 20 seconds). This extremely slow breathing rate produced rhythmic oscillations in blood pressure and heart rate that synchronized with the body’s natural cardiovascular rhythms, called Mayer waves. Trained practitioners naturally settled into a chanting pace that locked into these internal rhythms at a clean 1:2 ratio.
How to Chant Om
Sit comfortably with a tall spine. Take a deep breath in, then begin the sound on your exhale. Start with your mouth open, producing “ahh” from the back of your throat. Let it transition smoothly into “ooo” as your lips begin to round. Then close your lips for the “mmm,” feeling the hum resonate in your skull. After the sound ends, sit in the silence for a moment before inhaling again.
A common guideline is to spend about 80 percent of your exhale on the “A-U” portion (the open-mouth sounds) and only about 20 percent on the “M” (the hum). This keeps the sound expansive rather than cutting it short with the closed-lip vibration. You can chant as many rounds as you like. Three repetitions is traditional in many classes, but even a single Om can serve as a reset.
You don’t need to chant loudly. A gentle, sustained tone works. Some practitioners chant Om silently, repeating it internally during meditation. Both approaches are considered valid in the yoga tradition, though the physical vibration of audible chanting is what produces the measurable vagal and brain effects described in the research.