Pain
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Comparative Study
Individual differences in pain sensitivity: genetic and environmental contributions.
Large individual differences in pain sensitivity present a challenge for medical diagnosis and may be of importance for the development of chronic pain. Variance in pain sensitivity is partially mediated by genetic factors, but the extent of this contribution is uncertain. We examined cold-pressor pain and contact heat pain in 53 identical (MZ) and 39 fraternal (DZ) twin pairs, and 4 single twins to determine the heritability of the two phenotypes, and the extent to which the same genetic and environmental factors affect both pain modalities. ⋯ These findings demonstrate that cold-pressor pain and contact heat pain are mainly distinct phenomena from both a genetic and an environmental standpoint. This may partly explain disparate results in genetic association studies and argues for caution in generalizing genetic findings from one pain modality to another. It also indicates that differences in pain scale usage account for a minor portion of the variance, providing strong support for the validity of subjective pain ratings as measures of experienced pain.
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Comparative Study
Evidence for a biopsychosocial influence on shoulder pain: pain catastrophizing and catechol-O-methyltransferase (COMT) diplotype predict clinical pain ratings.
The experience of pain is believed to be influenced by social, cultural, environmental, psychological, and genetic factors. Despite this assertion, few studies have included clinically relevant pain phenotypes when investigating interactions among these variables. This study investigated whether psychological variables specific to fear-avoidance models and catechol-O-methyltransferase (COMT) genotype influenced pain ratings for a cohort of patients receiving operative treatment of shoulder pain. ⋯ A hierarchical regression model indicated that an interaction between pain catastrophizing and COMT diplotype contributed additional variance in pre-operative pain ratings. The pain catastrophizingxCOMT diplotype interaction demonstrated predictive validity as patients with high pain catastrophizing and low COMT activity (APS/HPS group) were more likely (RR=6.8, 95% CI=2.8-16.7) to have post-operative pain ratings of 4.0/10 or higher. Our findings suggest that an interaction between pain catastrophizing and COMT diplotype has the potential to influence pain ratings in patients seeking operative treatment of their shoulder pain.
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Comparative Study
Population-based cohort study of incident and persistent arm pain: role of mental health, self-rated health and health beliefs.
To investigate whether somatising tendency, low mood and poor self-rated health (SRH) predict incident arm pain, and whether these factors and beliefs about causation and prognosis predict symptom persistence, we conducted an 18-month postal follow-up in 1798 working-aged subjects, sampled from the registers of five British general practices. At baseline questions were asked about pain in the arm (lasting >or=1day in the prior 12months), mental health (Short-Form 36 (SF-36MH)), somatising tendency (the Brief Symptom Inventory (BSI)), SRH, and beliefs about causation and prognosis. At follow-up we asked about arm pain in the last four weeks, and whether it had been present on >or=14days. ⋯ Even stronger associations were found for arm pain on >or=14days. Persistent pain was significantly more common among those who attributed their pain to work or stress, and in those who expected symptoms still to be a problem in 12months. Thus, SRH and mental health indices were strong predictors of incident and persistent arm pain in adults from the community, while persistence was also predicted by beliefs about causation and prognosis.
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Comparative Study
Illness perceptions of low back pain patients in primary care: what are they, do they change and are they associated with outcome?
We describe the illness perceptions of patients with low back pain, how they change over 6 months, and their associations with clinical outcome. Consecutive patients consulting eight general practices were eligible to take part in a prospective cohort study, providing data within 3 weeks of consultation and 6 months later. Illness perceptions were measured using the Revised Illness Perception Questionnaire (IPQ-R). ⋯ There were strong, statistically significant, associations (RRs of 1.4 and over) between IPQ-R baseline consequences, timeline acute/chronic, personal control and treatment control scores and poor outcome. Patients who expected their back problem to last a long time, who perceived serious consequences, and who held weak beliefs in the controllability of their back problem were more likely to have poor clinical outcomes 6 months after they consulted their doctor. These results have implications for the management of patients, and support the need to assess and address patients' cognitions about their back problems.
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Comparative Study
Effects of stress on pain threshold and tolerance in children with recurrent abdominal pain.
Models of stress-induced hyperalgesia state that exposure to stress can exaggerate subsequent pain experiences. Studies using both animal and human subjects have shown evidence for hyperalgesia as a function of stress [e.g., Jorum E. Analgesia or hyperalgesia following stress correlates with emotional behavior in rats. ⋯ Children who underwent the stress tasks before the pain task exhibited lower levels of pain tolerance than those who received the pain task first (p<.01); no differences were found between the two groups in pain threshold or pain intensity ratings. Further, pain tolerance was not related to individual differences in physiological reactivity (heart rate change) to the stressor. The present research demonstrates the first evidence of the occurrence of stress-induced hyperalgesia in a pediatric pain population.