By Vivienne Parry in TIMESONLINE
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
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
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
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,
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;
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
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.