Psychological and behavioural correlates of acute and chronic congruent and incongruent low back pain

The purpose of the study was to examine how the psychological reactions to pain of acute low back pain (LBP) patients would compare to the psychological reactions to pain of chronic LBP patients who displayed signs and symptoms which were either congruent or incongruent with underlying anatomy and physiology. It was also of interest to examine whether negative cognitive and affective variables would mediate the expression of pain in these pain groups, and whether verbal and nonverbal facial measures of pain could be used to discriminate among pain groups. Subjects were assigned to the acute pain group if they had recurring or persistent pain for less than a three month period, and to the chronic pain group if they had recurring or persistent pain for longer than a three month period. The Pain Drawing (Ransford, Cairns & Mooney, 1976), the Nonorganic Physical Signs Assessment (Waddell, McCulloch, Kummell & Venner, 1980) and the Inappropriate Symptom Inventory (Waddell, Main, Morris, Di Paolo & Gray, 1984) were used to assign chronic pain patients to either the congruent or incongruent chronic LBP group. A physiotherapy protocol in which patients were asked to genuinely express pain, exaggerate and mask pain in response to a painful range of motion task was used to obtain a wide range of facial behaviour that would likely be relevant to understanding the expression of pain in these patient populations. Verbal reports of pain in response to the painful range of motion task, and in response to the pain that patients experienced on a daily basis were also examined. In addition, questionnaires concerned with coping strategies, worry and emotionality were used to tap cognitive and affective components of pain. Several demographic and patient pain related variables (e.g., medication use, disability, physical impairment) were also collected. The results of the study suggested that the acute and chronic incongruent pain patients had a similar psychological reaction to pain that was greater than the psychological reaction to pain of chronic congruent pain patients. In addition, the results suggested that the acute patients and chronic incongruent patients reported the unpleasantness of their pain to be similar, although only chronic incongruent patients differed significantly from chronic congruent patients. Acute and chronic incongruent patients were also similar on several demographic (socioeconomic status, compensation status) and pain related variables (regular use of opiate analgesics, and disability). Both groups differed significantly on the variables from the chronic congruent pain group. One final difference among groups was observed on a measure of physical impairment in which it was found that the chronic incongruent patients had the greatest physical impairment followed by the chronic congruent and acute pain patients. All differences among groups were significant. The most important variable for optimally discriminating among acute and chronic pain groups was physical impairment. This, however, may have been an artifact since the physical impairment measure was biased toward chronic pain patients obtaining higher scores. The most important variables for discriminating among chronic congruent and incongruent pain groups were related to the patient's negative interpretation of pain, compensation status, and reported regular use of painkillers. In general, all subjects reported the pain they experienced on a daily basis to be more intense and unpleasant than the pain they experienced in response to the painful leg movements. The facial actions that patients displayed when they were asked to genuinely express pain corresponded to facial expressions that have been found to be associated with pain in previous studies, and included brow lowering, orbit tightening, levator contraction, and mouth opening. Also consistent with previous research were findings suggesting that, although subjects were successful in masking and exaggerating pain, there were still some cues to deception apparent on the face.Arts, Faculty ofPsychology, Department ofGraduat