title: Expectations and positive emotional feelings accompany reductions in ongoing and evoked neuropathic pain following placebo interventions.
abstract: 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.
authors.affiliation: Department of Psychology and Behavioural Sciences, School of Business and Social Sciences, Aarhus University, Aarhus, Denmark Danish Pain Research Center, Aarhus University Hospital, Aarhus, Denmark Department of Cardiothoracic and Vascular Surgery, Aarhus University Hospital, Skejby, Denmark Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, UK Department of Neuroscience, Clinical and Applied Physiology Program, University of Turin Medical School, Turin, Italy Division of Neuroscience, Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville, FL, USA.
authors.forename: Gitte L
authors.initials: GL
authors.lastname: Petersen
authors.forename: Nanna B
authors.initials: NB
authors.lastname: Finnerup
authors.forename: Kasper
authors.initials: K
authors.lastname: Grosen
authors.forename: Hans K
authors.initials: HK
authors.lastname: Pilegaard
authors.forename: Irene
authors.initials: I
authors.lastname: Tracey
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Benedetti
authors.forename: Donald D
authors.initials: DD
authors.lastname: Price
authors.forename: Troels S
authors.initials: TS
authors.lastname: Jensen
authors.forename: Lene
authors.initials: L
authors.lastname: Vase
mesh_terms: D000328:Adult; D000368:Aged; D000779:Anesthetics, Local / Q000627:therapeutic use; D002211:Capsaicin / Q000008:administration & dosage; D004644:Emotions; D005260:Female; D006801:Humans; D008012:Lidocaine / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009437:Neuralgia / Q000523:psychology* / Q000628:therapy*; D064786:Nocebo Effect; D010147:Pain Measurement; D010812:Physical Stimulation; D015990:Placebo Effect; D011183:Postoperative Complications / Q000188:drug therapy* / Q000523:psychology*; D011581:Psychological Tests; D018689:Sensory System Agents / Q000008:administration & dosage; D013907:Thoracostomy / Q000009:adverse effects
chemical_list: D000779:Anesthetics, Local; D018689:Sensory System Agents; D008012:Lidocaine; D002211:Capsaicin
keywords: Emotional feelings; Expectation; Neuropathic pain; Nocebo hyperalgesia; Placebo analgesia