Summary of recommendations for future OLP studies
| Problem | Recommendation |
| Lack of adequate placebo controls | Treatment control groups (‘placebos’) should be structurally equivalent to OLP groups differing only in the factor(s) hypothesised to be therapeutically significant Waitlist controls, and treatment-as-usual may be employed but only in addition to adequate ‘placebo controls’ |
| Lack of clarity on how OLPs might work | Researchers should formulate clear hypotheses about how OLPs, including what they conjecture to be the active component of the treatment For example, if the mechanism of action is hypothesised to be: (a) The rationale: The OLP group might receive a statement including the rationale for the treatment; the placebo group should receive a statement without the rationale. Interactions should be the same for both groups (b) The quality of the clinician interaction: Interactions should be structurally equivalent between OLP and placebo groups (eg, same length, number, and content) but differ in the level of specific clinician behaviours (eg, level of empathy, confidence and so on). Judgements about the quality of interactions should be independently assessed (c) The action of taking pills: Participants should receive disclosures in closed envelopes. Both placebo and OLP groups might be informed: “the provision of placebo pills or emotional support and meeting regularly with a supportive individual may be helpful in eliciting powerful placebo effects’. Those allocated to the OLP group would also receive the instructions ‘placebo effects may be elicited by placebo pills and it is important to take the pills as prescribed’. Both groups should experience structurally-matched clinician interactions of the same quality of care which should be video-recorded and evaluated by independent assessors |
| Researcher bias | Researchers should be blind to patient allocation at all times to avoid investigator bias, and any potential bias relating to OLP treatment allegiance. Two independent assessors should be employed: one to measure primary outcomes, the other to look up the condition to which participant was assigned. If necessary, interactions should be conducted by clinicians blind to study hypotheses |
OLP, open-label placebo.