Table 1.

Taxonomy of procedures which could plausibly elicit placebo effects in non-malignant pain

Procedure derived from literature		Definition and use in research studies
Patient’s beliefs and characteristics
1.	Select patients based on treatment history	Screen and select patients (or subgroups) against inclusion criteria related to issues such as medical/treatment history, for example, naive to intervention being tested (not just contraindications).
2.	Create positive expectancy	Deliberately and explicitly suggest to patients that the intervention will be effective for them (not as part of informed consent process).
3.	Reduce negative expectancy*	The potentially negative or harmful procedures and characteristics of the treatment are deliberately minimised in information for patients.
4.	Convey a positive therapeutic message through informed consent procedures	Convey (verbally or in writing) a positive therapeutic message through the content of informed consent. The message might be explicit (eg, ‘this intervention is usually effective in most people’) or implicit (eg, ‘this treatment is an antihypertensive’).
5.	Harness sociocultural context*	Tailor the intervention according to the patient’s social and cultural context and history.
Practitioner’s beliefs and characteristics
6.	Practitioner expectancy	The person delivering the treatment expects it to be effective for the patient.
7.	Practitioner’s personal characteristics	The practitioner’s personal and/or professional characteristics (eg, status) are modified (through selecting practitioners with different characteristics) and/or emphasised to patients.
Healthcare setting
8.	Active recruitment	Actively seek out and recruit patients (eg, advertising for specific types of patients, writing personally to individual eligible patients identified through medical records).
9.	Active retention	Make patients feel valued by attempting to keep them in a study (eg, contact patients if they miss an appointment, incentivise attendance through monetary or non-monetary gifts).
10.	Follow-up	Assess patients after the intervention/experiment to assess long-term maintenance or changes in effects over at least 6 months.
11.	Follow a standardised protocol	The intervention is delivered according to a set, scientifically derived protocol, lending credibility to the intervention (and is therefore not individualised for each patient).
12.	Ethical oversight	Study practices and procedures are explicitly regulated and monitored by an institutional ethics committee, lending credibility to the intervention.
13.	Participating in research	Patients know that they are part of research and contributing to the furthering of human knowledge and/or improvement of healthcare for future patients.
14.	Symptom monitoring	Monitor patients’ symptoms using self-report measures, practitioner assessment or objective measures repeated over time at least twice; patients are aware of the resulting measurements.
15.	Enhanced environment*	The physical and interpersonal environment where the intervention is delivered is deliberately enhanced.
Treatment characteristics
16.	Sham intervention—medication	An inert substance is administered which is manufactured to appear identical to an active medication (eg, sugar pill, intravenous saline, topical agent).
17.	Sham interventions—physical	A sham physical intervention is administered which is designed to appear identical to the genuine intervention (eg, deactivated transcutaneous electrical nerve stimulation (TENS), non-penetrative acupuncture needles at non-acupuncture points).
18.	Sham interventions—attention only	Patients receive study-specific attention in terms of numbers of visits and time spent with study staff but no additional intervention.
19.	Ineffective substances*	Products unlikely to be effective or not indicated are administered (eg, vitamins in the absence of vitamin deficiency).
20.	Use salient side effects	Potential side effects are highlighted such that the patient can interpret them as evidence of a potent intervention.
21.	Matched treatments	To secure blinding, placebo/sham treatments are matched to ‘real’ treatments (eg, on mode of administration, dosage, frequency of administration, visual appearance, taste, smell, individual titration procedures).
22.	Maximised treatment procedures	The procedures and characteristics of the treatment are exaggerated, for example, through high dose, use of colour, high frequency, large pill size, lengthy duration of intervention, ritualistic administration.
23.	Conditioning	A desired response (eg, pain relief) is paired with an intervention stimulus (eg, placebo cream) so that the patient associates the response with the stimulus.
Patient–practitioner interaction
24.	The process of informed consent	The patient’s formal written and/or verbal informed consent is discussed and obtained.
25.	Detailed history	A detailed personal and/or medical and/or psychosocial history is obtained from the patient.
26.	Diagnosis/tests	Additional tests, examinations or confirmatory diagnostic procedures are undertaken to establish eligibility for the study.
27.	Care	The practitioner deliberately engages the patient with warmth, compassion and empathy.
28.	Patient-centred communication*	The practitioner adopts a style of consultation that they consider to be appropriate for a particular patient.
29.	Extra attention	The patient receives extra attention from being in the study, for example, is seen more frequently or for longer than usual.
30.	Continuity of care	Efforts are made for the same practitioner to see the same patient at each contact.

*Procedures added following survey of researchers.