The journal of pain : official journal of the American Pain Society
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Multiple investigators have recently asked whether neuroimaging has shown that chronic pain is a brain disease. We review the clinical implications of seeing chronic pain as a brain disease. Abnormalities noted on imaging of peripheral structures have previously misled the clinical care of patients with chronic pain. We also cannot assume that the changes associated with chronic pain on neuroimaging are causal. When considering the significance of neuroimaging results, it is important to remember that "disease" is a concept that arises out of clinical medicine, not laboratory science. Following Canguilhem, we believe that disease is best defined as a structural or functional change that causes disvalue to the whole organism. It is important to be cautious in our assertions about chronic pain as a brain disease because these may have negative effects on 1) the therapeutic dialogue between clinicians and patients; 2) the social dialogue about reimbursement for pain treatments and disability due to pain; and 3) the chronic pain research agenda. Considered scientifically, we may be looking for the cause of chronic pain through neuroimaging, but considered clinically, we are in fact often looking to validate pain complaints. We should not yield to the temptation to validate pain with the magnetic resonance imaging scanner (structural or functional). We should not see pain as caused by the brain alone. Pain is not felt by the brain, but by the person. ⋯ Neuroimaging investigators have argued that brain imaging may demonstrate that chronic pain is a brain disease. We argue that "disease" is a clinical concept and that conceiving of chronic pain as a brain disease can have negative consequences for research and clinical care of patients with chronic pain.
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There is a well-established comorbidity between migraine and anxiety and depression (A/D). Here, we investigate whether this relationship is specific for migraine and A/D or whether other types of pain are also consistently associated with A/D. In addition, we test whether there is a consistent association between migraine and other types of pain when comorbidity with A/D is controlled for. Data on A/D, migraine, and 6 nonheadache pain locations (back, neck, orofacial area, abdomen, joints, and chest) were analyzed in 2,981 participants from the Netherlands Study of Depression and Anxiety (NESDA). It was tested whether the prevalence of pain in each individual location, as well as the total number of pain locations, depended on A/D and migraine status. A/D was consistently associated with pain in all measured locations. Migraine was also associated with pain in all anatomical sites, but these associations weakened substantially after correction for A/D severity, suggesting that a considerable part of the comorbidity of migraine and other types of pain may be explained by A/D. These findings emphasize the importance of accounting for A/D in studies of pain comorbidity. This will contribute to a better understanding of the mechanisms underlying A/D and pain. ⋯ Anxiety and depression are consistently associated with pain, regardless of anatomical site. These disorders may be important factors in the co-occurrence of different pain disorders. Awareness of this comorbidity and a better understanding of the underlying mechanisms may facilitate adequate treatment of both types of conditions.