Expectations and positive feelings and neuropathic pain
Few studies have investigated mechanisms of placebo analgesia in neuropathic pain. In this study, an open-hidden design was used to investigate placebo and nocebo effects, in which patients received open and hidden administrations of pain-relieving (lidocaine) or pain-inducing (capsaicin) treatment controlled for the natural history of pain.
Eighteen patients with peripheral neuropathic pain 1-10 years prior to their participation were included. The open administration of Lidocaine and capsaicin was combined with a verbal suggestion for either pain relief or pain increase, respectively. The placebo and nocebo effects were calculated as the difference in pain levels between the open and the hidden administration of the pharmaceutics.
The results indicate large placebo effects, but no nocebo effects, for on-going and evoked pain. Expected pain levels predicted a substantial amount of the variance in pain intensity and unpleasantness in relation to the open administration of lidocaine. There was no effect of the active treatment alone, indicating that the observed findings may primarily be influenced by placebo-related factors optimizing the efficacy of the treatment including expectations and positive emotional feelings.
> From: Petersen et al., Pain (2014) (Epub ahead of print). All rights reserved to All rights reserved to Elsevier B.V.. Click here for the Pubmed summary.