Think your pain away : The neurochemistry of placebo analgesia

Sammanfattning: Placebo treatments are inert but are known to alleviate symptoms across numerous clinical conditions. One of the most studied placebo effects is placebo analgesia, which is a placebo effect limited to pain relief. This thesis aims to introduce the current state of research regarding the neuroscience of placebo analgesia and specifically to present research findings regarding the neurotransmission. Studies have demonstrated that placebo analgesia can be elicited through two separate processes interacting with each other; manipulation of expectations and through conditioning. These processes seem to affect neurotransmission in different ways. Many brain areas have been found to be correlated to placebo analgesia. Besides the pain-processing brain areas, studies point to that the prefrontal cortex can have a vital role in the placebo analgesic effect. Known neurotransmitters that have shown to be involved in placebo analgesia are endogenous opioids, cholecystokinin (CCK), and endocannabinoids. Studies point to that endogenous opioids are involved in the placebo analgesic effect when elicited by expectation or conditioned by an opioid drug. CCK act on placebo analgesia by affecting the release of endogenous opioids and endocannabinoids seem to be involved in placebo analgesia while it occurs due to conditioning with non-opioid drugs. Getting a better understanding of placebo analgesia and find ways to apply this knowledge in the clinical context could powerfully develop the whole medical society.