Pain
Pain is viewed as an unpleasant experience which often triggers a negative emotional response. The perception of pain is a subjective experience which occurs as a result of physical stimuli (McGrath, 1994). The concept of pain is complex as people can experience pain with little or no tissue damage or injury and, conversely, can suffer an injury without the presence of pain (McGrath, 1994).
Pain can be classified into three categories, acute, recurrent, or chronic. Acute pain is often thought of as an adaptive response to a noxious stimulus, in that
individuals learn to avoid situations which have caused physical harm in the past. It is brief in that it has a quick onset and reduces as the injury heals. Given that acute pain generally abates more quickly and does not cause prolonged pain or disruption to routine it does not normally result in long term emotional distress (McGrath, 2004). The pain experienced from a cold pressor test would be classified as acute pain. In contrast, recurrent pain refers to the experience of frequent periods of painful experiences, for example, migraine or tension headaches. Often recurrent pain is not caused by an underlying medical disorder, but rather the episodes of pain occur as a result of environmental factors of levels of stress (McGrath, 2004). Chronic pain is often caused by disease, injury and psychological factors. McGrath (2004) has suggested that chronic pain results from a number of noxious stimuli caused by the disease as well as treatments, with the specific source of the stimulation often unknown. Research has shown that the level of unpleasantness felt following a painful stimuli can be reduced if the individual has sufficient information about the painful stimuli, as well as the likelihood that they can avoid the stimuli (Price, Barrell, & Gracely, 1980).
It is important to recognise that pain perception can vary between children and adults. Both a child‟s age and level of development can influence their perception of pain (McGrath, 1990; Ross & Ross, 1988). The child‟s ability to understand pain, cope with the pain, and the impact of the pain all increase with age (Gafffney, 1993; Harbeck & Peterson, 1992). Furthermore, cognitive, behavioural and emotional factors can all have an important affect on a child‟s level of pain and distress (Ross & Ross, 1988).
The understanding of the underlying biological reactions to pain has developed over the years from the belief that the sensory system is relatively
simplistic, to the knowledge that it is a complex integrative system (McGrath, 2004; Wall & Melzack, 1994). The perception of pain relies on both excitatory and
inhibitory neural interactions. A number of psychological and emotional factors trigger activity in the descending pathways of the central nervous system, causing interactions between the nociceptive and non-nociceptive impulses in ascending pathways resulting in the perception of pain (McGrath, 1990; Price, 1988).
Research investigating pain sensitivity has shown those individuals who are highly sensitive to pain display more frequent and stronger activation of the primary somatosensory cortex, the prefrontal cortex, and the anterior cingulate cortex
(Coghill, McHaffie, &Yen, 2003). Pain sensitivity can be identified using reports from the individual in conjunction with psychophysiological data and functional magnetic resonance imaging (Coghill et al., 2003).
The nociceptive system is not rigid and passive, but has the potential to respond differently to different painful stimuli. Additionally, it is thought to be a plastic system wherein responses to the same level of tissue damage can change over time (McGrath, 1994). A number of factors influence how an individual‟s
nociceptive system will respond to injury or tissue damage. These factors can be further divided into stable factors which affect the way an individual interprets the pain sensations and variable factors which are influenced by context. Age, gender, level of cognitive ability, prior pain experiences, familial factors and cultural influences are all thought of as stable factors. In contrast, situational (e.g., expectation of the pain, level of control, relevance), behavioural (coping style, parental response, overt distress) and emotional factors (level of fear, anger and frustration) are thought to be dependent on context and have a significant effect on the perception of pain (McGrath, 1994).
An important factor in pain perception and sensitivity is stress. At times, stress can act to decrease pain sensitivity (al‟Absi & Petersen, 2003), while at other times stress can increase pain sensitivity (al‟Absi & Rokke, 1991). Stress-induced analgesia is thought to play an evolutionary role during times of high stress by assisting in the fight or flight response (Millan, 2002). Stress-induced hyperalgesia occurs as a result of increased vigilance to a threat in order to prevent potential harm (Martenson, Cetas, & Heinrichter, 2009). Research involving individuals with a history of childhood sexual abuse has shown they can develop both hyperalgesia in the form of fibromyalgia (Staud, Vierck, Cannon, Mauderli, & Price, 2001), and hypoalgesia which can be seen in some individuals with BPD (Bohus et al., 2004; Klossika et al., 2006).
The impact of psychological factors on the perception of painful stimuli has been widely studied. Situational variables including attention, level of predictability and relevance can directly alter the neural responses caused by noxious stimuli (Hayes, Dubner, & Hoffman, 1981). These situational factors do not only affect pain perception but also nociceptive activity (McGrath, 1994). A number of behavioural
factors are thought to increase the perception of pain including overt distress behaviours, inconsistent parental responses, prolonged emotional physical distress, lack of physical activity and a lack of peer and social activities (McGrath, 1993). There are also a number of emotional factors which have been shown to increase pain perception including anxiety and fear regarding diagnosis/treatment of an illness or disorder, general anxiety and stress, inability to identify and express emotions and high expectations for achievement (McGrath, 1993). The concept of pain will be further discussed in chapter five.