Individuals with chronic pain have the same response to placebo analgesia as healthy controls in terms of magnitude and reproducibility

It is unclear whether a diagnosis of chronic pain is associated with an increase or decrease in the placebo response. The aim of this study was to use an experimental placebo conditioning paradigm to test if expectancy for pain relief impacts on acute pain perception in individuals with a chronic pain diagnosis of osteoarthritis (OA) or fibromyalgia (FM), compared to healthy individuals (HI). An inert cream was applied to the dominant forearm of participants (60 OA, 79 FM and 98 HI), randomly assigned to either a placebo or control group. In both groups an inactive cream was applied to the dominant forearm. The placebo group was told this may or may not be a local anaesthetic cream, while the control group was told the cream was inactive. Laser pain was delivered, and numerical pain intensity ratings collected before, during and after cream application, along with expectation of pain relief and anxiety. The procedure was repeated two weeks later to assess reproducibility. There was a significant reduction in pain in the placebo group, independent of clinical diagnosis. Diagnostic groups (OA,FM,HI) did not differ in their magnitude of placebo analgesia or expectancy of pain relief. The results were similar in the repeat session. The results demonstrate that individuals with chronic pain respond to experimental placebo analgesia in a similar and reproducible manner as healthy individuals, despite higher levels of psychological co-morbidity. This has implications for utilising placebo analgesia in the treatment of chronic pain.