Available online 13 October 2023

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Placebo control is designed to evaluate the specific effect of one intervention. Relevant studies showed that acupuncture has a considerable placebo effect affected by many factors. In this paper, the relevant articles of acupuncture placebo studies all around the world were reviewed comprehensively to clarify the definition of acupuncture placebo effect and its psychological mechanism. The factors of acupuncture placebo effect were discussed in view of three aspects, i.e. types of sham acupuncture as control, patient-doctor interaction and outcome types. Eventually, the issues encountered in current studies of acupuncture placebo effect were described, e.g. lack of relevant studies especially with systematic and in-depth approaches in this field, inappropriate classification of specific non-needling effect relevant with acupuncture theory, and inaccurate assessment of acupuncture placebo effect due to the difficulty of sham-acupuncture design. In order to drive the future research direction of acupuncture placebo effect, it is suggested that more attention should be paid on the topic, including but not limited to correct recognition of the holistic effect of acupuncture, the appropriate design of sham acupuncture and in-depth research of mechanism of acupuncture placebo effect and its contributing factors.

Section snippetsPlacebo effect of acupuncture and its psychological mechanism

The placebo effect is widely presented in medical interventions. It is considered as the improvements in symptoms of participants after receiving treatment, which is attributable to the therapeutic ritual, treatment characteristics and doctor-patient interaction during treatment [6]. Differing from the real therapeutic effect, placebo effect results from the treatment-based contextual or environmental factors.

Acupuncture is an operational and complex intervention, with needles penetrating into

Factors influencing the placebo effect of acupuncture

The placebo effect of acupuncture has been recognized in early studies and the results of studies showed the considerable placebo effect [18,19,3,20,21]. In several meta-analyses and prospective RCTs, the comparison was made with multiple placebo controls for one individual disease. It was found that the effect of sham acupuncture was greater than that of the other placebo controls [18,19,3,20]. In one RCT [21], the sham acupuncture (non-penetrating type) was compared with placebo tablets to

Studies rarely touched acupuncture placebo effect and more are warranted

Taking “placebo effect” and “acupuncture” as keywords, 1123 articles were retrieved from the inception of PubMed database to 26th July 2023. After reading the abstract and full text of each article, 98 articles were included, with relevance to placebo effect of acupuncture (excluding sham acupuncture used as control, the studies on specific effect of acupuncture and the studies merely mentioned the phrase of sham acupuncture). Fig. 1 illustrates the publication year and numbers of the articles

Discussion

Acupuncture placebo effect is a core question in the evaluation of acupuncture effect. As a complex intervention, acupuncture has considerable placebo effect, and the patient's expectation may be the underlying psychological mechanism. The factors such as the types of sham acupuncture, patient-doctor interaction and outcome indicators affect the placebo effect of acupuncture and directly influence the assessment of the specific effect of acupuncture. In the coming studies, when designing the

Role of the funder/sponsor

The study sponsor had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

State of human/animal rights

No need to declare in this paper.

Data sharing statement

You can contact the corresponding author for the data.

CRediT authorship contribution statement

Yi-xuan XIE: Writing – original draft, Writing – review & editing. Zhi-yi XIONG: Writing – original draft. Cun-zhi LIU: Validation, Writing – review & editing. Shi-yan YAN: Supervision, Validation, Writing – review & editing.

Declaration of Competing Interest

The authors declare that there is no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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© 2023 Published by Elsevier B.V. on behalf of World Journal of Acupuncture Moxibustion House.