I know, that placebo can last as long as two years of sham therapy (1).
I found that for placebo duration three factors are necessary:
-positive beliefs and expectations on the part of the patient
-positive beliefs and expectations on the part of the physician
- a good relationship between the two parties (2).
But it is possible to end sham therapy and still have an effect? For example for one year?
Are there any studies focusing on this problem?
1) Efficacy and safety of finasteride therapy for benign prostatic hyperplasia: results of a 2-year randomized controlled trial (the PROSPECT study). PROscar Safety Plus Efficacy Canadian Two year Study.
2) Harnessing the power of the placebo effect and renaming it "remembered wellness".
Placebo effect is associated with the features of the central nervous system. "Winners heal faster than losers." This ancient thesis testifies to the importance of the individual characteristics of patients who are selected for observation. Please study the manuscripts in Attachment.
Placebo effect is related to nocebo effect and Hawthorne effect (that is briefly summarized as "observation changes behaviour"). It has more exoensively studies in CNS trials and brain areas involved are putetively know at least for some effect.
But basically I agree with your points that there are several components needed:: the physician-patient relationship, trust (or distrust in the case of nocebo effect), seeking relief, reward. However many other factors play a role such as general belief on specific therapies, feed back by other patients, previous experiences.
In some cases suche as Parkinson disease it has been shown that placebo effects activates specific circuitries with increase in dopamine secretion and symptoms improvements.
Below a couple of interesting readings
Great question!
In my experience in the lab, the duration of “placebo” self-healing effects will vary depending on several factors:
1) nature of the condition (e.g., placebo analgesia, or relief for nomologically controversial syndromes like iBS, or even depression, can last a very long time, and even lead to remission; less so, or not at all for ‘harder’ degenerative conditions — e.g., cancer, parkinson’s — from which only temporary relief from symptoms is to be expected
2) Personality differences, esp. suggestibility and other motivational factors pertaining to hope and positive expectancy. In our experience treating ADHD with a placebo mock brain scanner (see attached), oppositional children were the most treatment resistant.
4) Nature of placebo condition: e.g., the more elaborate, invasive and costly (motivationally, financially, time-investment) the procedure, the better it works, and the more likely to last long; the more *prestigious the condition the better (which is why we use "neuro" placebos of different kinds, given the high trust that people in our culture place on brain technology and brain-based explanatory models).
5) Conditioning. Several studies have shown that once a placebo response is conditioned (particularly with analgesia), even revealing the placebo condition to patients post hoc does not annul the effect. In our studies with mock scanners to treat ADHD, we first elicit relaxation and concentration effects using props and suggestion, then conditioning them outside the lab with a buzzing wristband after giving children the suggestion that each buzz will elicit the same effects. We then decrease the buzzing schedule until the no longer need it. We’ve had very good pilot results so far.
Of note:
Rather than a single effect and neurobiological mechanism, it is likely that changes in physiology and behaviour resulting from ‘placebo’ procedures recruit different neural pathways depending on the targeted medical conditions and expected outcomes. Subjects receiving placebos for chronic pain or irritable bowel syndrome, e.g., will experience different effects depending on what the context of the study or intervention leads them to expect. Here is a v. good definition of placebo effects (plural!) by Kapthuck and Miller — i.e.,, self-healing effects modulated by psychosocial, interpersonal, technological, and contextual cues that modulate positive expectancy and automatic response:
In a broad sense, placebo effects are improvements in patients' symptoms that are attributable to their participation in the therapeutic encounter, with its rituals, symbols, and interactions. These effects are … precipitated by the contextual or environmental cues that surround medical interventions. [These include] identifiable health care paraphernalia and settings, emotional and cognitive engagement with clinicians, empathic and intimate witnessing, and the laying on of hands.
https://www.nejm.org/doi/full/10.1056/nejmp1504023?page=2&
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4118664/
https://bmjopen.bmj.com/content/5/11/e009428
In the real world - placebo seems to have a long effect - otherwise why would homeopathy exist?
The magnitude of the placebo response varies considerably across categories of disorders
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