Robert Emery and Jim Coan professors of psychology at the University of Virginia, reply:
Terms such as “heartache” and “gut wrenching” are more than mere metaphors: they describe the experience of both physical and emotional pain. When we feel heartache, for example, we are experiencing a blend of emotional stress and the stress-induced sensations in our chest—muscle tightness, increased heart rate, abnormal stomach activity and shortness of breath. In fact, emotional pain involves the same brain regions as physical pain, suggesting the two are inextricably connected.
But how do emotions trigger physical sensations? Scientists do not know, but recently pain researchers uncovered a possible pathway from mind to body. According to a 2009 study from the University of Arizona and the University of Maryland, activity in a brain region that regulates emotional reactions called the anterior cingulate cortex helps to explain how an emotional insult can trigger a biological cascade. During a particularly stressful experience, the anterior cingulate cortex may respond by increasing the activity of the vagus nerve—the nerve that starts in the brain stem and connects to the neck, chest and abdomen. When the vagus nerve is overstimulated, it can cause pain and nausea.
Heartache is not the only way emotional and physical pain intersect in our brain. Reent studies show that even experiencing emotional pain on behalf of another person—that is, empathy—can influence our pain perception. And this empathy effect is not restricted to humans. In 2006 a paper published in Science revealed that when a mouse observes its cage mate in agony, its sensitivity to physical pain increases. And when it comes into close contact with a friendly, unharmed mouse, its sensitivity to pain diminishes.
Soon after, one of us (Coan) published a functional MRI study in humans that supported the finding in mice, showing that simple acts of social kindness, such as holding hands, can blunt the brain’s response to threats of physical pain and thus lessen the experience of pain. Coan implicated several brain regions involved in both anticipating pain and regulating negative emotions, including the right anterior insula (which helps to regulate motor control and cognitive functioning), the superior frontal gyrus (which is involved in self-awareness and sensory processing) and the hypothalamus (which links the nervous system to the endocrine system).
Although the biological pathways underlying these connections between physical and mental pain are not well understood, studies such as these are revealing how intricate the connection is and how very real the pain of heartache can be.
Pain is a simple enough concept to grasp. You stub your toe, shout, perhaps utter a few expletives, rub it better and it eventually fades. But neuroscientists are realising that pain is much more complex than anyone thought possible, comprising not just physical sensations, but emotional ones too. Pioneering studies are providing insights into why some people experience debilitating chronic pain long after an injury has healed, as well as why some are more prone to pain than others, and why certain people never recover from bereavement.
“Pain is much more than mere sensation. The psychological component is at least as important as the physiological processes giving rise to it,” says Dr Jonathan Brooks, a scientist at the Centre for Functional Magnetic Resonance Imaging of the Brain, at OxfordUniversity. His research centre scans the brains of people with chronic pain and compares them with those of healthy people.
While most pain goes away as an injury gets better, sometimes it remains for months or even years, long outlasting its original purpose. Chronic physical pain is debilitating and can cause disability, depression and post-traumatic stress disorder. It is also very common. A group from the University of Washington reported in the journal Archives of Surgery earlier this year that 63 per cent of patients who had sustained serious trauma still had injury-related pain a year later. It was most common in the 35-44 age group and in women, and least common in those with a college education.
Other chronic pain conditions include arthritis and lower back pain. In the latter, a physical source can be identified in only about 10 per cent of cases. No one really knows why some people experience chronic pain and others do not, but recent imaging studies at NorthwesternUniversity, Chicago, have found a series of abnormalities in the brains of chronic pain sufferers in which the part linked to decision-making (the prefrontal cortex) is reduced, while an area of the prefrontal cortex linked to emotion is hyperactive. What is known for certain is that the brain changes in those with chronic pain so that they experience pain differently from the way they did before.
We all have a system for suppressing pain when necessary so that we can flee attackers even when injured. Those who suffer from chronic pain appear unable to access this and cannot use distraction as a means of suppressing pain; their brains seem to amplify pain signals rather than inhibit them.
Treatment for the condition comprises both physical and psychological interventions, says Dr Michael Platt, the lead clinician for pain services at St Mary's Hospital, London, part of Imperial College Healthcare NHS Trust, where he holds weekly pain clinics. “Most physicians realise that you have to heal the mind as much as the body. For example, if you have pain, then depression is worse, and if you have depression, then pain is worse.” He adds that gaining a better indication of which parts of the brain are involved in pain sensations may lead to better treatments for patients.
We all respond to pain differently
Scientists are increasingly realising that everyone responds to pain differently. “There are many physiological and psychological factors that determine how much pain you feel,” says Dr Brooks. “Personality, how worried a person is, and, in the case of women, the time in the menstrual cycle, can all have an effect.”
He adds that our genes can also influence our sensitivity to pain. This was first brought to the attention of scientists by the “ginger-whinger” syndrome. Anaesthetists reported that redheaded women complain of pain more than other patients, and consequently need more pain relief. Why? Not because redheads are wimps; it was later discovered that their genetic make-up makes them less sensitive to certain types of pain medication.
Neuroscience is also revealing a host of similarities between emotional and physical pain. In the same way that in some people injury can cause long-lasting chronic pain, science reveals why some will never get over heartbreak.
Professor David Alexander, the director of the Aberdeen Centre for Trauma Research, has been involved in many disasters: the 2004 tsunami; Iraq; and the recent earthquake in Pakistan. He is not surprised about the link between physical and emotional pain. “If you listen to people who are damaged emotionally, they will often translate their pain into physical similes: ‘my head is bursting, my guts are aching', and so on. The parallel is very strong.”
It is only in the past few years, however, that scientists have begun to investigate what is going on in the brain during an episode of emotional pain. The neuroscientist Mary Frances O'Connor, of the University of California, Los Angeles (UCLA), is one of the scientists who has propelled emotional pain up the research agenda. “We're at a very new time when we can use technologies to look at the brain and the heart.” Naomi Eisenberger, one of her colleagues at UCLA, has shown which parts of the brain are active when we feel emotional pain. She devised a computer game in which participants were made to feel left out. Simultaneous brain scanning revealed that the pain of being socially rejected was processed in much the same way in the brain as physical pain, and in the same area, the anterior cingulate cortex, which is located towards the front of the brain, roughly at the height of the temples.
Eisenberger theorises as to why this should be so. Pain is often interpreted as a warning, so that you take your hand away from a hot surface. Social relationships are crucial to our survival as a species. In dangerous situations, a lone human being is in peril, whereas a group may survive. “The social attachment system piggybacked on to the physical pain system to make sure that we stay connected to close others,” Eisenberger says. Being wrenched from another or rejected by a group is painful, so we learn to avoid it.
A related issue is “complicated grief”, which O'Connor estimates occurs in about 10 per cent of people, who fail to adapt to bereavement over time. Her imaging work shows that this sort of grief activates neurons in the reward centre of the brain, giving addictive-like properties to memories of the lost one. There is a strong suspicion, as yet unproven, that sufferers might also be among those who experience the greatest levels of chronic physical pain. This is an area that deserves urgent research because of its terrible emotional and physical toll.
Pain caused by emotional distress is more deeply felt and longer lasting than that caused by physical injuries, according to a new study.
In a finding that calls into question the old saying that "sticks and stones may break my bones, but words will never hurt me", psychologists used four experiments to discover how people get over emotional or physical pain.
In their paper "When Hurt Will Not Heal: Exploring the Capacity to Relive Social and Physical Pain", the authors propose recent discoveries suggesting social or emotional pain is as real and intense as physical pain.
The researchers asked participants to relive their past painful experiences by writing in detail what had happened and how they had felt.
In the first two studies, students were asked to relive both emotional and physical pain, answering a series of questions and then recalling in detail an experience of physical injury, or an experience of betrayal by a person who was close to them, or both.
Each experience was to have occurred in the previous five years.
The students were asked to note how long ago the event happened, how much it hurt at the time, how many times they had talked about the experience, and how painful the experience felt now.
Participants in the emotional pain condition reported higher levels of pain than participants in the physical pain condition, found the researchers from Purdue University in the US and Macquarie University and the University of New South Wales in Australia.
The students also reported less pain when they relived the experience than they had reported before writing the account.
In experiments three and four participants were given cognitive tasks with different levels of difficult after reliving a socially or physically painful event.
Again, those in the emotional pain condition performed worse than those thinking about physical injury.
One of the authors, Dr Kip Williams from Purdue, said: "While both types of pain can hurt very much at the time they occur, social pain has the unique ability to come back over and over again, whereas physical pain lingers only as an awareness that it was indeed at one time painful.
"Why aren't we always suffering pain by recollections of social betrayal and other forms of social pain? Because we are pretty good at keeping these memories at bay.
"We had to induce our participants to think about the details of the social painful event in order to get them to feel pain at the present. Merely saying, 'oh yeah, my boyfriend cheated on me once...' is insufficient to cause current pain. They have to steep themselves in the memory, and that's something we don't ordinarily do."
The results are published in the August 2008 issue of the journal Psychological Science
