Figure 1: Imagining a healing white light might actually precipitate the body's own capacity to deliver pain relief (e.g. opioids), but won't reduce the size of a cancerous tumour.
Placebo-activated opioids, for example, not only relieve pain; they also modulate heart rate and respiration. The neurotransmitter dopamine, when released by placebo treatment, helps improve motor function in Parkinson's patients. Mechanisms like these can elevate mood, sharpen cognitive ability, alleviate digestive disorders, relieve insomnia, and limit the secretion of stress-related hormones like insulin and cortisol.
In one study, Benedetti found that Alzheimer's patients with impaired cognitive function get less pain relief from analgesic drugs than normal volunteers do. Using advanced methods of EEG analysis, he discovered that the connections between the patients' prefrontal lobes and their opioid systems had been damaged. Healthy volunteers feel the benefit of medication plus a placebo boost. Patients who are unable to formulate ideas about the future because of cortical deficits, however, feel only the effect of the drug itself. The experiment suggests that because Alzheimer's patients don't get the benefits of anticipating the treatment, they require higher doses of painkillers to experience normal levels of relief...
...one way that placebo aids recovery is by hacking the mind's ability to predict the future. We are constantly parsing the reactions of those around us—such as the tone a doctor uses to deliver a diagnosis—to generate more-accurate estimations of our fate. One of the most powerful placebogenic triggers is watching someone else experience the benefits of an alleged drug. Researchers call these social aspects of medicine the therapeutic ritual. [Italics added] Link
This is the first time I've considered the intimate relationship between mental time travel and the placebo effect. The mental time travel hypothesis supposes that the same memory system (episodic) which allows us to vividly recollect past events is also activated when we anticipate future events. The research above suggests that patients who lack the cognitive capacity to consider the future also fail to show placebo benefits.
If this is true, then new age remedies such as visualization, meditation or hypnosis may have successful impacts on patients. Simple activities such as imagining or recollecting comfort and peacefulness could affect placebogenic triggers for pain relief.
Similarly, people who struggle to construct vivid mental images or lack empathy for the experience of fictional characters, may also be less susceptible to placebogenic triggers.