Practicing a specific type of guided slow breathing every day for eight weeks reduces the body’s physical fight-or-flight response to mental stress in veterans dealing with post-traumatic stress disorder. The findings suggest that consistent breathing exercises might help protect the long-term cardiovascular health of people with trauma-related mental illness. The study was published in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology.
Post-traumatic stress disorder is a severe mental health condition that develops after a person experiences a terrifying event. People dealing with this condition face a much higher risk of developing high blood pressure and heart disease later in life. This elevated risk is tied to the way the condition alters the autonomic nervous system, which controls involuntary bodily functions.
The autonomic nervous system is broadly divided into two branches. The sympathetic branch acts like a gas pedal to trigger the fight-or-flight response, while the parasympathetic branch acts as a brake to calm the body down. Individuals with trauma disorders often experience an overactive sympathetic nervous system, meaning their foot is constantly hovering over the physiological gas pedal.
When exposed to mental stress, these patients often exhibit exaggerated physical reactions. They experience rapid spikes in blood pressure and an onslaught of electrical impulses traveling through their sympathetic nerves. Over time, these intense physical reactions cause physical wear and tear on the heart and blood vessels.
Medications that dampen this nerve activity exist, but they often cause unwanted side effects. Some of these drugs are poorly tolerated and have metabolic impacts that can actually worsen cardiovascular risks. Medical professionals are searching for alternative, drug-free ways to calm the nervous system in this vulnerable population.
One potential intervention is device-guided slow breathing. This technique involves using an electronic biofeedback tool to help a person gradually slow their breathing rate. Previous research showed that a single session of this guided breathing briefly lowered blood pressure and nerve activity in trauma patients while they were actively doing the exercise.
Ida T. Fonkoue, a researcher at the Emory University School of Medicine and the Atlanta Veterans Affairs Medical Center, led a team to investigate whether these benefits could be sustained. The researchers wanted to see if daily practice over two months would permanently lower resting heart rates, blood pressure, and resting nerve activity. They also wanted to test if the breathing routine would dampen the body’s physical reaction to sudden mental stress.
The research team recruited 25 military veterans who had post-traumatic stress disorder and slightly elevated blood pressure. The participants were randomly assigned to one of two groups for an eight-week trial. Neither the researchers nor the participants knew who was placed in which group.
One group used an active guided breathing device for fifteen minutes every day at home. The machine used sensors strapped around the abdomen and musical tones in headphones to help users lower their breathing rate to about five or six breaths per minute. The second group used an identical machine that played similar music.
Instead of guiding the second group to breathe slowly, this placebo device kept them at a normal resting rate of about fourteen breaths per minute. Before the trial began, the researchers invited all participants to the laboratory for extensive baseline testing. They measured resting blood pressure, heart rate, and overall respiratory rates in a quiet room.
To directly measure the fight-or-flight response, the team used a specialized technique to track electrical signals in the sympathetic nerves. They inserted a microscopic tungsten wire into a prominent nerve in each participant’s leg. This allowed them to count the exact number of nerve impulses traveling toward the muscle tissue in real time.
The researchers also tested the body’s natural blood pressure regulation system, known as the baroreflex. They did this by administering drugs through an intravenous line to artificially raise and lower blood pressure over a short period. They watched how the brain adjusted the heart rate and nerve signals to compensate for the sudden changes.
Finally, they tested how the participants reacted to an acute mental challenge. The veterans were asked to perform rapid mental math. They subtracted numbers in their head for three minutes while study staff in white coats urged them to go faster and be more accurate, a proven way to induce mental stress.
After eight weeks of practice at home, the participants returned to the laboratory to repeat the entire battery of tests. The researchers found that the daily breathing exercises did not alter the participants’ resting heart rate or resting blood pressure. Resting nerve activity also remained entirely unchanged in both groups.
The body’s blood pressure regulation system did not improve, and post-traumatic stress symptoms did not ease in either group. In other words, the daily intervention did not seem to provide a permanent, round-the-clock calming effect on the body’s physiological baseline. But when the researchers looked at the mental math test results, they noticed a distinct difference in how the nerves reacted.
For the group using the placebo device, the mental math stressor triggered the same high rate of nerve impulses as it did at the beginning of the study. For the group practicing the slow breathing exercises, the body responded differently. Their nerve activity spiked much less intensely during the mental math test than it had eight weeks prior.
The results indicate that long-term use of guided slow breathing can fundamentally alter how the sympathetic nervous system handles sudden stress. Even when the veterans were not actively using the breathing machine, their fight-or-flight nerves remained calmer under pressure. The researchers suggested this might help shield the cardiovascular system from the harmful effects of daily psychiatric stress.
Oddly, this dampened nerve reaction did not translate into lower blood pressure during the math test. Blood pressure spiked just as high in the slow-breathing group as it did in the placebo group. The researchers suspect other biological mechanisms, such as floating hormones or changes in blood vessel dilation, might be driving the blood pressure spikes independently of the nerve impulses.
The study had a few limitations that might affect how broadly the conclusions can be applied. The participant pool was relatively small and consisted primarily of African American male veterans. The biological responses to the breathing exercises might look slightly different in women or in civilian populations.
The team also only measured nerve activity directed toward the skeletal muscles. They could not determine if the breathing technique reduced nerve activity directed toward other organs like the heart or kidneys. A short period of abstaining from certain psychiatric medications before testing might also not have been long enough to clear the drugs from the participants’ systems entirely.
Moving forward, researchers need to conduct larger trials to see if these nervous system changes actually translate into lower rates of heart disease over time. Future investigations might also look into whether the breathing exercises reduce underlying inflammation in patients with trauma disorders. Studies exploring how the practice affects heart rate variability over longer periods could also provide deeper insights into the body’s stress response.
The study, “Eight weeks of device-guided slow breathing decreases sympathetic nervous reactivity to stress in posttraumatic stress disorder,” was authored by Ida T. Fonkoue, Yingtian Hu, Toure Jones, Monica Vemulapalli, Justin D. Sprick, Barbara Rothbaum, and Jeanie Park.