Professor TJ Ryan
Last updated: Sep 2004
Keywords: wound healing; perception of pain; mental activity; pain management.
The nervous system transmits the sensations of itch and pain as well as messages from the brain that prompt the individual to move away from potential harm. Human beings have developed the ability to imagine such sensations and responses, as they might occur, far into the future or in fantasises. Since the nerve endings release agents that can inflame and affect cell behaviour even the imagination can affect remarkable tissue responses.
People have been interested in the impact of mental activity on pain and wound healing for many years. In 1951, Kepecs examined the impact of emotion on exudation in wounds . More recently Kiecolt-Glaser  has suggested that psychological stress can suppress healing and could have important clinical implications. Despite the fact that much of this knowledge is not new, further work is required in this area to develop these concepts and to incorporate them into everyday practice.
Transmission of information from the nerves in the periphery (ie skin) to nerves in the spinal cord, midbrain and higher centres of the fore brain is mediated by the release of chemicals and electrical impulses. There are frequent sites along the nerve, both peripherally and centrally, where these mediators can be inhibited or enhanced by stimuli from other nerves or agents. Such interference is normally used to filter out stimuli that are continuous or of a constant intensity, for example the sensations of breathing, contraction of the heart or peristalsis of the gut. Environmental noise, taste and vision are also subject to filtering through interference. This filtering process is reduced at the beginning and end of a stimulus, which allows an individual to be only aware of the sensation of wearing clothes as they are put on or taken off.
Signals from the nerve endings in the periphery are subject to filtering at any point as messages are distributed through the spinal cord and the mid brain. In addition, the mental processes of the cerebral cortex can enhance or suppress these signals. As such, the sensation of pain can be modified by interference at many points from the nerve ending situated in an injured epidermis to the frontal cortex of the brain.
Pain can be defined as 'an unpleasant sensory and emotional (conscious) experience associated with actual or potential tissue damage' ( www.isap-pain.org). Although unpleasant, experiencing pain is important for a variety of reasons: in the first instance it acts as a warning of harm, but it will also give rise to a number of physiological responses. The best known of these is axon flare (activated through the axon reflex), which causes vasodilation, reddening and increased sensitivity of the skin surrounding an injured area (triple response). This immediate physical response to injury and pain is important in initiating the processes necessary for repair.
Everyday experience suggests a clear link between attention and perception of pain, whereby the level of pain experienced is often less or absent if the individual's attention is diverted at the time of injury. Conversely, most people find that the pain experience is worse if they are anxious. The human brain has foresight and as a consequence can anticipate and be motivated to avoid pain, but it can also imagine pain and be deluded.
For some, disassociation from pain is possible. For example, hypnosis has been used for many years as a form of pain relief during activities such as body piercing, although how it works is not fully understood. Chapman et al  have also studied the suppression of inflammation by hypnosis.
Hypnosis is thought to induce a reduced awareness of self and a state of deep relaxation that abolishes responses attributed to anxiety. This also appears to be the case in certain religious ceremonies where ritualistic chanting and skilled techniques allow apparently pain-free body piercing with larger implements such as swords. In this instance, the state of mind that allows injury without pain also appears to suppress inflammation, reduce bleeding and allow healing with reduced scarring  .
Conversely, there are extremely painful conditions such as reflex sympathetic dystrophy and phantom limb syndrome (also known as complex regional pain syndrome) ,  that manifest with increased awareness, a high degree of anxiety, increased bleeding, inflammation and impaired healing. In such cases it appears that the mechanisms for filtering continuous pain of a constant level are dysfunctional, whereby the inflammatory effects of nerve impulses and the release of chemical mediators are not 'switched off'. In cases of phantom limb pain, attempts have been made to trick the individual's brain into thinking that the limb has not been amputated through the use of mirrors to reflect the remaining limb so that it appears in the place of the one removed . Unfortunately success has been limited and in some cases, as reported to the author, this approach appears to have resulted in more confusion for the individual.
The relationship between anxiety, pain and bleeding is complex: deep states of relaxation (such as that created during hypnosis) may play a role in the suppression of pain and inflammation, while other mental states can result in exacerbation of pain and wounding, for example psychogenic purpura (painful bruising syndrome) , . This condition predominantly presents in women and is characterised by widespread, painful bruising. It is not associated with coagulation defects and there is usually a psychiatric history.
Another condition worth mentioning is the development of stigmata. People who suffer from stigmata appear to be able to localise triple response reactions and bleeding to those sites relating to the crucifixion of Christ. Pain and anxiety are prominent features in all reported cases and, where the wounds are persistent or recurrent, there is fragility and incomplete healing  .
In recent years, quality of life studies have led to improved management of pain. As well as raising awareness of the possible consequences of pain, such studies have contributed to an understanding of how practitioners can prescribe for specific patterns of pain. For example, stabbing pain may respond to anti-epileptic therapy while pain that is deep and poorly localised, such as might be felt in cases of diabetic neuropathy and post-herpetic neuralgia, frequently responds to tricyclic antidepressants such as amitriptyline . Hyperaesthesia to mild stimuli such as stroking is, however, unlikely to respond to paracetamol, aspirin or non-steroidal antiflammatory drugs despite the fact that these are often used as effective first-line agents for inflammation in which the principal elements are localised pain and swelling with heat, and where the pain is an appropriate response to injury. Pain with fever or other signs of infection may be treated most effectively with antibiotics, once the causative organism has been identified. When the principal effect of pain is that it disturbs sleep, a mild sedative may be all that is required.
This author would like to suggest that alternative methods of pain management should be considered in the future management of patients with wounds. At present morphine and related agents tend to be under prescribed, particularly where the pain is a result of local injury.
In addition, several devices are available that aim to inhibit continuous pain, particularly that of constant intensity. These work by firing electrical impulses at selected sites in the nervous system, in particular, at the level of the spinal cord.
Further methods include exercises that control mental activity, for example. Other more spiritual approaches such as hymn singing and Gregorian or Buddhist chanting may also be appropriate for some individuals.
Advances in technology have allowed non-invasive measurement of brain activity. Further investigation in this area will allow greater insight into how and whether approaches such as hypnosis work and provide guidance on how these methods can be used effectively.
The significance of pain in wound healing is a much neglected area. Taking an accurate history of the pain experienced by a patient and prescribing rationally should be mandatory for all clinicians. In addition, an improved understanding of the role of mental activity may lead to better management strategies.
However, the answers for the palliation of pain do not lie simply in the lower levels of the nervous system, but also in the 'spirit'. An individual's perception of pain is not separate to the perception of everything else and some of the most intense suppression or enhancement of pain is to be found linked to religious belief.
Finally, the way forward in pain and wound management should be effective multidisciplinary working to manage the range of physiological, pathological, emotional, psychological, cognitive, environmental and social factors involved.
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