Evidence indicates that stimulating the vagus nerve can help people with epilepsy, diabetes, treatment-resistant depression, and post-traumatic stress disorder – as well as inflammatory autoimmune conditions like Crohn’s disease or rheumatoid arthritis.
“It can sound sort of magical with all the things it does,” said Eric Porges, an assistant professor in the department of clinical and health psychology at the University of Florida who studies the vagus nerve. Our understanding of the vagus nerve “continues to grow in richness and depth,” he said.
In the early 2000s researchers started to show that vagus nerve stimulation could help some patients who were severely depressed and had not responded to other treatments.
A wave of studies followed.
By 2005, the Food and Drug Administration had approved implantable pulse-generating devices that sent electrical signals to the vagus nerve, for use in patients with treatment-resistant depression. Similar devices have also been approved by obesity – to help control feelings of hunger and fullness – and for the treatment of epilepsy.
Researchers are now recruiting patients for the largest clinical trial to date examining to what degree vagus nerve stimulation may help patients with depression who have been unable to find relief with other treatments.
Implanting a device may be especially helpful for those with bipolar depression because so few treatments exist for them, said Dr. Scott Aaronson, one of the senior psychiatrists involved in the clinical trial and the chief science office of the Institute for Advanced Diagnostics and Therapeutics.
Implanted vagus nerve stimulation isn’t currently accessible for most people, however, because insurers have declined to pay for the procedure, with the exception of Medicare recipients participating in the latest clinical trial.
Dr. Tracey’s research, which uses internal vagus nerve stimulation to treat inflammation, may also have applications for psychiatric disorders like PTSD, said Dr. Andrew H. Miller, the director of the Behavioral Immunology Program at Emory University, who studies how the brain and the immune system interact, and how those interactions can contribute to stress and depression.
PTSD is characterized by increased measures of inflammation in the blood, he said, which “can influence circuits in the brain that are related to anxiety.”
In one pilot study at Emory, for example, researchers electronically stimulated the neck skin near the vagus in 16 people, eight of whom received vagus nerve stimulation treatment and eight of whom received a sham treatment. The researchers found that the stimulation treatment reduced inflammatory responses to stress and as associated with a decrease in PTSD symptoms, indicating that such stimulation may be useful for some patients, including those with elevated inflammatory biomarkers.
How is nerve activity measured?
The activity of the vagus nerve is difficult to measure directly, especially given how complex it is. But because some vagus nerve fibers connect with the heart, experts can indirectly measure cardiac vagal tone – or the way in which your nervous system regulates your heart – by looking at your heart rate variability – which has been associated with conditions like diabetes, heart failure, and hypertension.
A high variability between heartbeats may signify an ideal vagal tone.
Can vagal tone be improved?
Holding your breath and submerging your face in cold water can trigger the “diving reflex,” a response that slows the heartbeat and constricts blood vessels. Some people who have tried it report that it has a calming effect and even reduces insomnia. Others wrap an ice pack in a cloth and place it on their chest to relieve anxiety.
These specific exercises haven’t been sufficiently studied as methods for controlling anxiety or depression, so it is difficult to know if they work, or if they do, how well. Even so, some experts say they’re worth a shot.
“It’s certainly one of the more benign things you can do,” Dr. Aaronson said.
But Dr. Tracey urgent caution, adding that it’s difficult to properly assess the risks and benefits without clinical data. “I would not advise anyone to do any intervention without checking with their physician,” he said.
“For wellness, try to maintain high vagus nerve activity through mindfulness, exercise, and paced breathing,” Dr. Tracey said. “These are all very good for you.”
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