Many ailments have a stress-related component, as the purpose of our stress response is to handle an immediate threat, diverting energy away from long-term task

Many ailments have a stress-related component, as the purpose of our stress response is to handle an immediate threat, diverting energy away from long-term tasks like healing, fighting infection etc. A placebo is a reassurance, that we don't need to worry, we are being looked after, protected, safe, and everything will be ok. Thus, the immune system gets its resources back, and gets on with its job. We heal. sorry, no references, just seems a simple explanation of the observed evidence (eg so strong that double-blind experimental design is required to prevent it confounding drug test results).