Most people have had the experience of pushing their bodies beyond what seems possible – to run an extra kilometre in a race or to carry a heavy load of shopping bags. To prevail they exert mind over body, ignoring messages of pain or fatigue.
Some scientists now believe the same may be possible for health and well-being. They report a link between thinking and such physical and emotional indicators as inflammation, heart attacks and self-esteem. The connection helps explain why people sometimes see an improvement in their health when they take remedies that have no medicinal value – the so-called placebo effect.
The key to this rich mind-body link is the vagus nerve, which runs from the brain through the body via the lungs, heart, stomach and digestive tract. It also connects to nerves involved in speech, eye contact and facial expression. The vagus nerve forms an essential part of the parasympathetic nervous system, which is responsible for calming organs after the stressed “fight or flight” adrenalin response to danger. The stronger this vagus activity, the faster the body relaxes after stress to resume digestive and other functions.
The strength of a person’s response is known as vagal tone. Those with a higher vagal tone enjoy a vast range of benefits in addition to being calm and quick to de-stress. Studies show that they can better regulate their blood glucose levels, reducing incidence of diabetes, stroke and cardiovascular disease. They are also socially and psychologically stronger – happier, better able to concentrate and remember things, more empathetic, less prone to depression and more likely to have close friendships. In contrast, low vagal tone is associated with a range of physical and psychological health risks.
Vagal tone is measured by using an electrocardiogram to look at the difference in heart rate when breathing. Inhaling temporarily suppresses the vagal nerve, increasing the heart rate to speed the transport of oxygenated blood in the body. Exhaling does the opposite, slowing the heart rate. The bigger the difference, the higher the vagal tone.
Though vagal tone is to a certain extent predetermined genetically, low ones are more prevalent in people who are obese and rarely exercise. Barbara Fredrickson and Bethany Kok, two psychologists from the University of North Carolina at Chapel Hill, wondered if people could change their mindset and “think” their way to a higher vagal tone.
In 2010 they recruited 70 people for an experiment in which each volunteer was asked to rate the strength of positive and negative emotions such as joy, love, anger and disgust every day. Vagal tone was measured at the beginning and end of the experiment, nine weeks later. Half of the participants were taught a meditation technique that aims to promote feelings of goodwill toward themselves and others.
The results were encouraging. Those who meditated showed a significant rise in vagal tone, reporting an increase in positive emotions. However, people who started with the lowest vagal tone showed the smallest increase, suggesting that those most in need of “thinking themselves better” were having the hardest time doing so.
There is also what Kok calls an “amplification effect.” Once a person has raised his or her vagal tone it becomes easier to increase it further because a higher tone promotes greater feelings of connectedness and well-being.
Kok, now at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, is trying to replicate the results in a much larger trial. If she succeeds, vagal tone could be used as a diagnostic tool for various health issues. “Hospitals already track heart-rate variability – and hence vagal tone – in patients who have had a heart attack,” she says. “We know that low variability is a risk factor, but we’re still a long way from using vagal tone more widely. We don’t even know yet what a healthy vagal tone looks like – we’re just looking at ranges.” The vagus nerve can be stimulated with an implant, but this would be invasive (see Electrifying effects, p. 38). Studies also show that vagal tone increases with exercise, and there is some evidence that simply listening to uplifting music may have the same effect. Thanks to the vagus nerve, physical well-being may be in your head.
There is no cure for such common chronic inflammatory diseases as rheumatoid arthritis and coeliac disease (which affects the bowel). Treatments involve systemic medication with a range of side effects. Now a few pilot studies are attempting to take a neurologic approach.
A handful of patients have had a device implanted in their necks that electrically stimulates their vagus nerve. “It is early on, but so far the results have been very promising,” says Ulf Andersson, professor of immunology at Karolinska University Hospital in Sweden, who studies the link between the vagus and inflammation. “In a Dutch study still underway, eight out of 10 patients with rheumatoid arthritis have responded well – in fact, at the end they don’t want the implant removed.”