Citation
Zaccaro A, Piarulli A, Laurino M, Garbella E, Menicucci D, Neri B, Gemignani A. How Breath-Control Can Change Your Life: A Systematic Review on Psycho-Physiological Correlates of Slow Breathing. Front Hum Neurosci. 2018 Sep 7;12:353. doi: 10.3389/fnhum.2018.00353. PMID: 30245619; PMCID: PMC6137615.
4 FUNDAMENTALS
1. Essential Background Material
(Note: I think this paper wins “Best Title Ever” award, lol. Ok, on with the 411.)
There has been a lot of research on meditation and its underlying physiology and associated cognitive benefits. It’s also been used extensively in preclinical and clinical conditions.
Simultaneously, we know that breathing is intertwined with meditative practices, often serving as an anchor for our focus. Moreover, ancient contemplative practices understood that the breath and mind are closely linked. For example, the Hatha Yoga Pradipika states, "When the Breath wanders, the mind is unsteady, but when the Breath is still, so is the mind still.”
Modern science also recognizes many health benefits of breath control (specifically slow breathing), such as reduced stress and anxiety. However, the breath-mind connection was largely overlooked when this paper was published. Most studies had focused on how meditation affects the mind rather than pure breathing practices.
Thus, unraveling the effects of breathing versus other meditative practices remained unanswered.
This review aimed to fill that gap by synthesizing the scientific literature on slow breathing and psychological/behavioral outcomes. They were trying to answer the following question: What physiological changes are common among pure slow breathing studies showing improvements in psychological results (like less stress & anxiety)?
2. What Did this Research Do?
They found studies that used slow breathing (<10 breaths/min) without other mental components (such as breath counting or breath awareness). They only included studies with healthy individuals to not muddle the results with condition-specific results.
Their focus was on studies that had physiological measurements accompanying behavioral outputs. For example, if someone felt calmer, there needed to be physiological measurements that might explain that improvement in mood. The physiological measurements they focused on were brainwave activity, heart rate variability (HRV), respiratory sinus arrhythmia (RSA), and cardio-respiratory synchronization.
After using some rigorous criteria for their literature search (see the paper if you’re interested), they ended up with 15 studies that met the inclusion criteria.
3. What Were the Major Findings?
As it is with science, there was nuance and many contradictory results. However, a few common themes did emerge.
First, slow breathing was associated with increases in HRV, particularly in the low frequency (LF) band. Second, it was also associated with increases in RSA. These two results indicate increased activity in the parasympathetic (rest-and-digest) branch of the nervous system. Moreover, slow breathing was also associated with increases in alpha brainwave activity (brainwaves thought to be associated with “flow”) and decreases in theta brainwave activity.
Critically, these common physiological changes observed during/after slow breathing were associated with improved psychological and behavioral outcomes. For example, slow breathing generally increased relaxation while reducing anxiety, depression, and anger.
Lastly, they examined the importance of the nose. They reviewed studies showing that nasal breathing directly correlates with brain activity. For instance, certain areas of the brain show oscillations synchronized with nasal (but not mouth) breathing.
Based on the evidence, the authors hypothesize that the nose is the link between slow breathing, brain, autonomic functioning, and positive emotional outcomes.
4. Why Do These Results Matter?
This review provides the physiological mechanisms of slow breathing that improve behavioral outcomes. Thus, it shows that slow breathing (independent of meditation, yoga, etc.) can be a powerful way of changing our physiology to promote positive psychological outcomes.
Moreover, these results are significant because they give us breathing nerds a grounded basis for explaining how slow breathing helps: it increases parasympathetic action (which helps with relaxation, anxiety, etc.) and enhances alpha brainwave activity (which facilitates focus, attention, etc.).
1 BIG TAKEAWAY
Altogether, slow breathing consistently increases HRV, RSA, and alpha brainwave activity. These physiological changes are associated with better psychological and behavioral outcomes.
1 PRACTICAL APPLICATION
From a practical perspective, most studies showing improved HRV and RSA used breathing rates of about 5-6 breaths/min (although some were as high as 9 breaths/min).
The studies showing increased alpha brainwave activity used slower rates of 3-4 breaths/min (although one used a 10 breath/min rate).
Lastly, the studies used different inhale-to-exhale ratios: either an equal or slightly longer exhale.
So, to apply these findings in your life, grab your favorite breathing app and set it to a comfortable pace for you, between 3-10 breaths/min. Use an equal ratio or a slightly longer exhale. Practice regularly to increase HRV, RSA, and alpha brainwave activity, and ultimately improve your overall mood.