http://www.medicalnewstoday.com/articles/179671.php"The evidence behind placebo effects and the clinical and ethical considerations are examined in a review in this week's edition of The Lancet. The analysis is the work of Damien G Finniss, University of Sydney Pain Management and Research Institute, Royal North Shore Hospital, Sydney, Australia, and colleagues.
The authors comment: "For many years, placebos have been defined by their inert content and their use as controls in clinical trials and treatments in clinical practice. Recent research shows that placebo effects are genuine psychobiological events attributable to the overall therapeutic context, and that these effects can be robust in both laboratory and clinical settings. There is also evidence that placebo effects can exist in clinical practice, even if no placebo is given."
The fact that there is not one placebo effect but many is a fundamental conclusion in the review. Mechanistically, there are very different placebo effects. Meaning that, the psychosocial situation of a patient when they receive a treatment can be very influential in changing a person's physiology.
Many mechanisms have been identified from the psychological viewpoint. They include:
• expectations about the effect of a treatment
• desire for symptom relief
• several learning processes such as classical conditioning and social observation
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Another piece of another puzzle, but much more research needs to be done, and ethics of the matter need to be explored. And...