title: Placebo manipulations reduce hyperalgesia in neuropathic pain.
abstract: Several studies have shown that placebo analgesia effects can be obtained in healthy volunteers, as well as patients suffering from acute postoperative pain and chronic pain conditions such as irritable bowel syndrome. However, it is unknown whether placebo analgesia effects can be elicited in chronic pain conditions with a known pathophysiology such as a nerve injury. Nineteen patients who had developed neuropathic pain after thoracotomy were exposed to a placebo manipulation in which they received either open or hidden administrations of lidocaine. Before the treatment, the patients rated their levels of spontaneous pain and expected pain and completed a questionnaire on their emotional feelings (Positive Affect Negative Affect Schedule) and went through quantitative sensory testing of evoked pain (brush and cold allodynia, heat pain tolerance, area of pinprick hyperalgesia, wind-up-like pain after pinprick stimulation). The placebo manipulation significantly reduced the area of pinprick hyperalgesia (P=.027), and this placebo effect was significantly related to low levels of negative affect (P=.008; R(2)=0.362) but not to positive affect or expected pain levels. No placebo effect was observed in relation to spontaneous pain or evoked pain, which is most likely due to low pain levels resulting in floor effects. This is the first study to demonstrate a placebo effect in neuropathic pain. The possible mechanisms underlying the placebo effects in hyperalgesia are discussed, and implications for treatment are outlined.
authors.affiliation: Department of Psychology, Aarhus University, Aarhus, Denmark Danish Pain Research Center, Aarhus University Hospital, Aarhus, Denmark Department of Cardiothoracic and Vascular Surgery, Aarhus University Hospital, Skejby, Denmark 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 Laue
authors.initials: GL
authors.lastname: Petersen
authors.forename: Nanna Brix
authors.initials: NB
authors.lastname: Finnerup
authors.forename: Kathrine Næsted
authors.initials: KN
authors.lastname: Nørskov
authors.forename: Kasper
authors.initials: K
authors.lastname: Grosen
authors.forename: Hans K
authors.initials: HK
authors.lastname: Pilegaard
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Benedetti
authors.forename: Donald D
authors.initials: DD
authors.lastname: Price
authors.forename: Troels Staehelin
authors.initials: TS
authors.lastname: Jensen
authors.forename: Lene
authors.initials: L
authors.lastname: Vase
mesh_terms: D000368:Aged; D000698:Analgesia / Q000379:methods; D059350:Chronic Pain / Q000188:drug therapy* / Q000503:physiopathology / Q000523:psychology; D004644:Emotions / Q000502:physiology; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy* / Q000503:physiopathology / Q000523:psychology; D008297:Male; D008875:Middle Aged; D010149:Postoperative Pain / Q000188:drug therapy* / Q000503:physiopathology / Q000523:psychology; D015990:Placebo Effect; D010919:Placebos / Q000008:administration & dosage*; D013908:Thoracotomy / Q000009:adverse effects
chemical_list: D010919:Placebos