The placebo response might be important in clinical practice, but it is certainly difficult to study and the findings of such investigations can be confusing. This seems to be exemplified by two new trials.
The first study examined the possibility of using theatrical performance tools, including stage directions and scripting, to reproducibly manipulate the style and content of a simulated doctor-patient encounter and influence the placebo response (defined as improvement of clinical outcome in individuals receiving inactive treatment) in experimental pain.
A total of 122 healthy volunteers were exposed to experimental pain using the cold pressor test and assessed for pain threshold and tolerance before and after receiving a placebo cream from a “doctor” impersonated by a trained actor. The actor alternated between two distinct scripts and stage directions. One script emulated a standard doctor-patient encounter (scenario A), while the other emphasized elements present in ritual healing such as attentiveness and strong suggestion (scenario B).
The placebo response size was calculated as the % difference in pain threshold and tolerance after exposure relative to baseline. Subjects demonstrating a ≥30% increase in pain threshold or tolerance relative to baseline were defined as responders. Each encounter was videotaped in its entirety.
Inspection of the videotapes confirmed the reproducibility and consistency of the distinct scenarios enacted by the “doctor”-performer. Furthermore, scenario B resulted in a significant increase in pain threshold relative to scenario A. This increase derived from the placebo responder subgroup; as shown by two-way analysis of variance (performance style, F = 4.30; p = 0.040; η(2) = 0.035; style × responder status interaction term, F = 5.21; p = 0.024) followed by post hoc analysis showing a ∼60% increase in pain threshold in responders exposed to scenario B (p = 0.020).
Performance style and response size in placebo responders and non-responders. Bars represent mean ± SE of % change in CPT threshold of 60 subjects in scenario A: 53 non-responders vs. 7 responders and 62 subjects in scenario B: 51 non-responders and 11 responders. Two-way ANOVA by performance style and responsiveness revealed significant effects of doctor’s performance (F = 4.30; p = 0.040; η2 = 0.035) and responsiveness (F = 134.71; p < 0.001) as well as a significant interaction term (F = 5.21; p = 0.024). ∗p = 0.020, Fisher’s least significant difference post hoc test.
The authors concluded that these results support the hypothesis that structured manipulation of physician’s verbal and non-verbal performance, designed to build rapport and increase faith in treatment, is feasible and may have a significant beneficial effect on the size of the response to placebo analgesia. They also demonstrate that subjects, who are not susceptible to placebo, are also not susceptible to performance style.
In the second study, the authors investigated if an implicit priming procedure, where participants were unaware of the intended priming influence, affected placebo analgesia.
In a double-blind experiment, healthy participants (n = 36) were randomized to different implicit priming types; one aimed at increasing positive expectations and one neutral control condition. First, pain calibration (thermal) and a credibility demonstration of the placebo analgesic device were performed. In a second step, an independent experimenter administered the priming task; Scrambled Sentence Test. Then, pain sensitivity was assessed while telling participants that the analgesic device was either turned on (placebo) or turned off (baseline). Pain responses were recorded on a 0-100 Numeric Response Scale.
Overall, there was a significant placebo effect (p < 0.001), however, the priming conditions (positive/neutral) did not lead to differences in placebo outcome. Prior experience of pain relief (during initial pain testing) correlated significantly with placebo analgesia (p < 0.001) and explained 34% of placebo variance. Trait neuroticism correlated positively with placebo analgesia (p < 0.05) and explained 21% of placebo variance.
The authors concluded that priming is one of many ways to influence behaviour, and non-conscious activation of positive expectations could theoretically affect placebo analgesia. Yet, we found no SST priming effect on placebo analgesia. Instead, our data point to the significance of prior experience of pain relief, trait neuroticism and social interaction with the treating clinician.
The two studies are similar but generate somewhat contradictory results. In the discussion section, the authors of the first paper stress that “replication of our findings in clinical populations; employing professional physicians of both sexes, are necessary in order to establish their generality and possible application in medical training, with the aim of improving patient outcome across diseases and treatment modalities.” This is certainly true. They continue by stating that “future studies using performance tools in clinical trial settings could demonstrate the potential of borrowing performance principles and techniques from traditional healing and applying them to physician–patient encounters in Western medicine, following certain necessary modifications. Performance tools could thus eventually be incorporated into the systematic training of physicians and medical students, possibly to complement programs in Narrative Medicine and Relational Medicine.”
These ideas are not dissimilar to what we have been discussing on this blog repeatedly. For instance, I have previously tried to explain that “the science and the art of medicine are essential elements of good medicine. In other words, if one is missing, medicine is by definition not optimal. In vast areas of alternative medicine, the science-element is woefully neglected or even totally absent. It follows, that these areas cannot be good medicine. In some areas of conventional medicine, the art-element is weak or neglected. It follows that, in these areas, medicine is not good either.”
The fact that the two studies above show contradictory findings is not easy to interpret. Possibly, this shows how fragile the placebo response can be. It can be influenced by a multitude of factors related to an experiment or the clinical setting. If that is so, and placebo effects are truly unreliable, it would be yet another argument for not relying on them in clinical routine. In my view, clinicians should try to maximize them where they can. Yet placebo effects are not normally a justification for employing placebo therapies in clinical practice. In other words, the fact that a bogus treatment can generate a placebo response is not a good reason for using it on patients who need help.
Good clinicians have probably always been good ‘performers’. Alternative practitioners tend to be excellent ‘performers’, and I am sure their success is mainly due to this ability. I see little reason why conventional practitioners should not (re-)learn the skills that once upon a time were called ‘good bed-side manners’. Maximizing the placebo effect in this way might maximize the benefit patients experience – and for that we do not require the placebo-therapies of alternative medicine.