Do deep breathing exercises help with stress?

When encountering stress, the brain activates the sympathetic nervous system and the hypothalamic-pituitary-adrenal system.¹ This involves releasing stress hormones and activating the immune system, which can result in a variety of physical responses, including increased heart rate, increased respiratory rate, and muscle tension. These adaptive responses can help increase alertness and decrease reflex time, improving the chances of surviving a potentially life-threatening stressful situation. After the stress passes, the body returns to its normal baseline. However, when stress responses are prolonged or excessive, they can lead to deleterious effects on physical and mental health.^2-4

Deep breathing exercises can be an effective strategy to reduce stress levels through the control of stress-mediated rises in respiratory rate and blood pressure. The Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH) endorse breathing exercises as an effective stress management and coping technique.^5,6 While breathing exercises vary, most involve breathing air into the lungs, holding the breath, and exhaling air in a controlled, deliberate fashion. They often also include aspects of mindfulness, such as visualizing stress being released from the body with each exhale. Some examples of breathing exercises include box breathing, slow breathing, and diaphragmatic breathing.

A 2023 systematic review and meta-analysis of 15 studies found that various types of breathing exercises have a significant effect on blood pressure and heart rate.⁷ On average, systolic blood pressure decreased by 7.06 mmHg (95% Confidence Interval [CI] [3.92-10.20], p<0.01) and diastolic blood pressure decreased by 3.43 mmHg (95% CI [1.97-4.89], p<0.01). On average, heart rate also decreased by 2.41 beats per minute (95% CI [0.30-4.53], p=0.03). Some of the breathing exercises studied were slow breathing, music-guided breathing, Pranayamas, alternate nostril breathing, and Yogic breathing exercises.

A 2019 meta-analysis of 17 studies found that slow breathing exercises, whether guided by a device or self-guided, reduce blood pressure significantly.⁸ On average, systolic blood pressure decreased by 5.62 mmHg (95% CI [3.38-7.86]) and diastolic blood pressure decreased by 2.97 mmHg (95% CI [1.66-4.28]). There was also a non-significant decrease in heart rate reported in seven studies.

A 2017 randomized controlled trial of 39 information technology (IT) workers in Beijing found that deep breathing exercises decreased respiratory rate and salivary cortisol levels. Among the 19 participants undergoing an intervention of 20 sessions of deep breathing exercises over eight weeks, respiratory rates dropped from a mean of 9.95 breaths per minute to 3.45 breaths per minute versus the control group, which actually increased from 14.82 breaths per minute to 17.51. Within the intervention arm, cortisol levels dropped from 6.25 nmol/L at baseline to 5.00 nmol/L after eight weeks compared to control, which increased from 5.75 nmol/L at baseline to 6.00 nmol/L.⁹

Another 2017 randomized controlled trial of 38 college-aged participants studied the effects of weekly deep breathing exercises on physiologic and psychologic metrics of stress.¹⁰ Nineteen participants were assigned to an intervention of weekly, 90-minute, guided deep breathing sessions compared to 19 controls, whom sat weekly for 90 minutes with no intervention. Findings indicated that self-reported stress, heart rate, and salivary cortisol levels significantly decreased in the intervention arm over the course of ten weeks. The intervention arm reported lower levels of stress, assessed by the Measurement of Psychological Stress (MSP) Scale. Mean MSP levels in the intervention arm dropped from 100 at baseline to 90 at five weeks and 83 at ten weeks, compared to control, which stayed relatively stable (93, 88, and 96). Heart rate dropped from 99 beats per minute (BPM) at baseline to 90 BPM at five weeks and 85 BPM at ten weeks, compared to 93, 88, and 97 BPM among controls. Mean salivary cortisol levels dropped from 9.62 pg/mL at baseline to 9.53 pg/mL after five weeks and 7.34 pg/mL after ten weeks in the intervention arm, versus the control arm, which stayed relatively stable at 9.55, 9.53, and 9.58 pg/mL.

Similarly, a 12-week randomized controlled trial of 99 healthy, young adult male participants assigned half (n=49) to breathing exercise training and half (n=50) assigned to no intervention.¹¹ Perceived stress scores were significantly lower in the intervention arm, falling from 21.2 at baseline to 17.2 at 12 weeks (decrease of 3.59 vs 0.44 in control). Heart rate and blood pressure also had statistically significant differences, although absolute changes were marginal (heart rate decreased by 1.16 BPM for intervention vs 0.54 for control; systolic blood pressure decreased by 1.18 mmHg vs 0.50 mmHg; diastolic blood pressure decreased by 0.78 mmHg vs 0.10 mmHg).

A 2023 randomized controlled trial (n=108) examined the psychophysiological effects of various types of breathing exercises compared to mindfulness meditation on mood, anxiety, and resting heart rate, heart rate variability, and sleep.¹² Participants were randomly assigned to one of three types of breathing exercises (cyclic sighing, box breathing, or cyclic hyperventilation with retention) or mindfulness meditation as the comparator. Both mindfulness meditation and breathing exercises had a similar significant effect on self-reported mood and anxiety measured by positive and negative affect schedule (PANAS, ranges from 10-50; average daily increase in positive mood 1.22 for mindfulness, 1.91 for breathing exercises; average daily decrease in negative mood 1.62 for mindfulness, 0.98 for breathing exercises) and State-Trait Anxiety Inventory (STAI, ranges from 20-80; average daily reduction 3.95 for mindfulness, 3.03 for breathing exercises). Cyclic sighing improved mood (PANAS 1.89 ± 3.76, p < 0.0001) more than mindfulness meditation (PANAS 1.22 ± 2.34, p = 0.06). There were no significant changes in heart rate variability, resting heart rate, or sleep among any groups. Of the 91 participants who completed a debrief questionnaire, 90% found the breathing exercises helpful while 10% found them boring or burdensome.

While current medical practice guidelines may not recommend breathing exercises over other stress reduction strategies to address life and workplace stressors, the existing evidence suggests that breathing exercises may be a beneficial tool to counter stress with minimal risks or resources required.

References

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6. Stress. U.S. Department of Health & Human Services. Accessed July 26, 2023. https://www.nccih.nih.gov/health/stress
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9. Ma X, Yue ZQ, Gong ZQ, et al. The Effect of Diaphragmatic Breathing on Attention, Negative Affect and Stress in Healthy Adults. Front Psychol. 2017;8:874. doi:10.3389/fpsyg.2017.00874
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11. Naik GS, Gaur GS, Pal GK. Effect of Modified Slow Breathing Exercise on Perceived Stress and Basal Cardiovascular Parameters. Int J Yoga. Jan-Apr 2018;11(1):53-58. doi:10.4103/ijoy.IJOY_41_16
12. Balban MY, Neri E, Kogon MM, et al. Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Rep Med. Jan 17 2023;4(1):100895. doi:10.1016/j.xcrm.2022.100895