Expectations and positive emotional feelings accompany reductions in ongoing and evoked neuropathic pain following placebo interventions

• Published in: Pain (Amsterdam) Vol. 155; no. 12; pp. 2687 - 2698
• Main Authors: Petersen, Gitte L., Finnerup, Nanna B., Grosen, Kasper, Pilegaard, Hans K., Tracey, Irene, Benedetti, Fabrizio, Price, Donald D., Jensen, Troels S., Vase, Lene
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Elsevier B.V 01.12.2014; International Association for the Study of Pain; Elsevier
• Subjects: Adult; Aged; Anesthetics, Local - therapeutic use; Biological and medical sciences; Capsaicin - administration & dosage; Emotional feelings; Emotions; Expectation; Female; Humans; Lidocaine - therapeutic use; Male; Medical sciences; Middle Aged; Nervous system (semeiology, syndromes); Nervous system as a whole; Nervous system involvement in other diseases. Miscellaneous; Neuralgia - psychology; Neuralgia - therapy; Neurology; Neuropathic pain; Nocebo Effect; Nocebo hyperalgesia; Pain Measurement; Physical Stimulation; Placebo analgesia; Placebo Effect; Postoperative Complications - drug therapy; Postoperative Complications - psychology; Psychological Tests; Sensory System Agents - administration & dosage; Thoracostomy - adverse effects; Emotional feelings; Expectation; Placebo analgesia; Nocebo hyperalgesia; Neuropathic pain; Affect affectivity; Analgesia; Nervous system diseases; Treatment; Placebo; Emotion emotionality; Hyperalgesia
• ISSN: 0304-3959; 1872-6623; 1872-6623
• DOI: 10.1016/j.pain.2014.09.036

Large placebo but not nocebo effects were seen in ongoing and evoked neuropathic pain, and patients’ expectations about these treatments coexisted with emotional feelings. Research on placebo analgesia and nocebo hyperalgesia has primarily included healthy subjects or acute pain patients, and it is unknown whether these effects can be obtained in ongoing pain in patients with chronic pain caused by an identifiable nerve injury. Eighteen patients with postthoracotomy neuropathic pain were exposed to placebo and nocebo manipulations, in which they received open and hidden administrations of pain-relieving (lidocaine) or pain-inducing (capsaicin) treatment controlled for the natural history of pain. Immediately after the open administration, patients rated their expected pain levels on a mechanical visual analogue scale (M-VAS). They also reported their emotional feelings via a quantitative/qualitative experiential method. Subsequently, patients rated their ongoing pain levels on the M-VAS and underwent quantitative sensory testing of evoked pain (brush, pinprick, area of hyperalgesia, wind-up-like pain). There was a significant placebo effect on both ongoing (P=.009 to .019) and evoked neuropathic pain (P=.0005 to .053). Expected pain levels accounted for significant amounts of the variance in ongoing (53.4%) and evoked pain (up to 34.5%) after the open lidocaine administration. Furthermore, patients reported high levels of positive and low levels of negative emotional feelings in the placebo condition compared with the nocebo condition (P⩽.001). Pain increases during nocebo were nonsignificant (P=.394 to 1.000). To our knowledge, this is the first study to demonstrate placebo effects in ongoing neuropathic pain. It provides further evidence for placebo-induced reduction in hyperalgesia and suggests that patients’ expectations coexist with emotional feelings about treatments.