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. 2026 Feb 15;35(4):e70280. doi: 10.1111/jsr.70280

Placebo Effect of Sham Acupuncture for Primary Insomnia: A Meta‐Analysis of Randomised Controlled Trials

Bo Jiang 1, Yi‐Nan Wang 1, Jun Zhang 2, Hong‐Ru Li 2, Pei‐Wen Xue 1, Juan Li 1,✉, Rong‐Jiang Jin 1,✉
PMCID: PMC13357979  PMID: 41692996

ABSTRACT

To provide updated evidence from randomised controlled trials (RCTs) on the placebo effect size and influencing factors of sham acupuncture for primary insomnia. A systematic literature review and meta‐analysis were conducted in accordance with the PRISMA guidelines. Databases such as PubMed, Cochrane, Embase, Web of Science, China National Knowledge Infrastructure, Wanfang, China Science and Technology Journal Database and Chinese Biological Medicine Database were searched, focusing on sham acupuncture and primary insomnia. RCTs would be included if they compared the clinical efficacy of sham acupuncture before and after the intervention in patients with primary insomnia. The risk of bias of the included studies was evaluated using the Cochrane risk‐of‐bias tool (version 2.0). A total of 4348 studies were retrieved, and 36 eligible randomised controlled trials were included. The overall risk of bias in 13 studies were considered as high risk, 7 studies were categorised as some concerns and 16 studies were considered as low risk. The results of the meta‐analysis showed that sham acupuncture significantly reduced Pittsburgh Sleep Quality Index (PSQI) [weighted mean difference (WMD) = 1.38, (95% confidence interval (CI) = 0.90, 1.86), p < 0.05] and Insomnia Severity Index (ISI) [WMD = 2.58, (95% CI = 1.46–3.69), p < 0.05]. There was no significant change in polysomnography and actigraphy. Sham acupuncture had a certain placebo effect in clinical trials of primary insomnia. The placebo effect varied from different types of sham acupuncture.

Keywords: meta‐analysis, placebo effect, primary insomnia, sham acupuncture

1. Introduction

Primary insomnia (PI) is a sleep disorder characterised by difficulty initiating or maintaining sleep, or non‐restorative sleep, for at least 1 month. Unlike secondary insomnia, PI is not directly attributable to other medical, psychiatric, or environmental causes (Shekleton et al. 2010). The cause of PI is often multifactorial, including physiological, psychological and behavioural factors. Epidemiological investigation showed that the weighted prevalence rates of insomnia‐related symptoms occurring at least three times per week were as follows: difficulty initiating sleep (14.0%), difficulty maintaining sleep (28.3%), premature awakening (32.1%) and non‐restorative sleep (39.9%) (Chung et al. 2015). The prevalence of insomnia is on the rise, affecting up to 30% of the population, with a particularly notable increase in the incidence of acute insomnia, reaching 27% within a 1‐year timeframe (Perlis et al. 2020). The survey of Chaput et al. (2023) indicated that the economic burden of insomnia in Canada for the year 2021 was $1.9 billion, constituting 1.9% of the overall disease burden cost in the country for the same year. This disease has emerged as a significant public health issue globally. In contemporary medical practice, the management of insomnia predominantly involves pharmacological interventions and cognitive‐behavioural therapy for insomnia (CBT‐I) (Morin and Buysse 2024). Pharmacological treatment for insomnia is associated with a range of adverse effects, including xerostomia, dizziness, asthenia, somnolence during daytime and memory impairment, thus its long‐term use is limited (Freund and Weber 2023). CBT‐I is the frontline treatment approach; nevertheless, it encounters certain constraints in practical application. Currently, there is a scarcity of adequately trained therapists specialising in CBT‐I, which fails to satisfy the demand of the patient population (Manber et al. 2012; Koffel et al. 2018). Furthermore, the complexity and economic burden associated with CBT‐I can impede patient adherence, leading to a high rate of treatment discontinuation due to these factors (Freund and Weber 2023; Koffel et al. 2018; Knutzen et al. 2024). In clinical settings, acupuncture serves as an adjunctive treatment modality, demonstrating beneficial therapeutic effects on diverse forms of insomnia (Gao and Zhou 2024). In recent years, an increasing number of clinical trials investigating the efficacy of acupuncture for insomnia have incorporated sham acupuncture controls to validate that the therapeutic benefits of acupuncture are not attributable to placebo effects (Yin et al. 2017; Zhang, Qin, et al. 2023).

Sham acupuncture refers to a placebo treatment where needles are inserted into non‐acupoint locations or are not inserted at all, simulating the experience of acupuncture without delivering its intended therapeutic effects (Xie, Liu, et al. 2023). Previous meta‐analyses (Liu et al. 2020; Xu et al. 2024; Kim et al. 2021) have demonstrated the efficacy of acupuncture in the treatment of insomnia. Compared to sham acupuncture controls, the therapeutic effect of acupuncture reflects a combination of both specific mechanisms and non‐specific placebo effects. A network meta‐analysis result indicates that acupuncture is superior to traditional western medicine in improving Pittsburgh Sleep Quality Index (PSQI) scores (Wang et al. 2023). The latest evidence indicates (Zhao et al. 2024) that acupuncture has a significant effect in reducing the overall scores of sleep scales such as PSQI and Insomnia Severity Index (ISI). The objective parameters of sleep monitoring further confirmed the effectiveness of acupuncture, showing a shortened sleep latency, an increased total sleep time and an improved sleep efficiency. However, in clinical trials assessing acupuncture efficacy, the utilisation of various sham acupuncture types may introduce variability within the control group outcomes, consequently impacting the overall trial results. This heterogeneity can complicate the interpretation of findings and the generalisability of study replications (Macpherson et al. 2014; Zeng et al. 2022; Zhang et al. 2016). We aim to quantify the placebo effect of sham acupuncture in PI treatment and identify its key influencing factors. Our goal is to determine which sham acupuncture method acts as a more credible placebo control, ultimately establishing a reference standard for the design of robust clinical trials in acupuncture for PI.

2. Methods

This study was conducted according to the A Measurement Tool to Assess Systematic Reviews (AMSTAR 2.0) (Shea et al. 2017) and reported in accordance with the preferred reporting items for systematic reviews and meta‐analyses (PRISMA) guidelines. The study protocol was registered at PROSPERO (CRD 42024567311, available at PROSPERO (york.ac.uk)).

2.1. Search Strategy

Two reviewers independently (B.J. and J.Z.) searched the following databases: PubMed, Cochrane Library, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang data, China Science and Technology Journal Database (CSTJ) and Chinese Biological Medicine Database (CBM) from their inceptions to March 19, 2025. Moreover, we also searched websites of randomised controlled trials (RCTs) registration (ClinicalTrials.gov and (chictr.org.cn)). A systematic search strategy was developed using Boolean operators to combine Medical Subject Headings (MeSH) and free‐text terms. The strategy was tailored to the specific requirements of each database. The complete search strategies for all databases are shown in Appendix S1. In addition, relevant experts were consulted for potential studies.

2.2. Inclusion Criteria

Studies fulfilled all the following inclusion criteria would be included: (1) patients were diagnosed PI according to standard operational diagnostic criteria (the 2nd and the 3rd edition of Chinese Mental Illness Diagnostic Standard [CCMD‐2/CCMD‐3]) (Chen 2002; Psychiatry CAOM 1995), the 10th revision of the International Classification of Disease [ICD‐10] (World Health Organization 1992), the 4th and 5th edition of Diagnostic and Statistical Manual of Mental Disorders [DSM‐IV and DSM‐V] (American Psychiatric Association 1994, 2013), the 2nd and 3rd edition of International Classification of Sleep Disorders [ICSD‐2 and ICSD‐3] (Sateia 2014; Thorpy 2012); (2) interventions included acupuncture, electroacupuncture, auricular acupuncture, thumbtack needle; (3) conventional treatment involved sham acupuncture or sham electroacupuncture; (4) the primary outcome was the PSQI. Secondary outcomes included ISI, Fatigue Scale‐14 (FS‐14), sleep efficiency (SE), sleep awakening (SA), total sleep time (TST), sleep inset latency (SOL), wake after sleep onset (WASO), rapid eye movement (REM) and other relevant outcomes; (5) the study design was RCT.

2.3. Exclusion Criteria

Studies that met any of the following criteria would be excluded: (1) secondary insomnia; (2) the data were unavailable through various approaches; (3) duplicate publications; (4) non‐Chinese and English literature; (5) animal studies.

2.4. Study Selection

Endnote X9 was used to manage the retrieved records. After removing duplicates, two independent reviewers (B.J. and J.Z.) screened the titles and abstracts to identify potential studies. Subsequently, the rest of the records were scrutinised in full text. Any inconsistency was resolved through consultation with the third reviewer (J.L. or R.‐J.J.).

2.5. Data Collection and Extraction

Two independent reviewers (B.J. and P.‐W.X.) extracted data from included studies with a standard extraction form. The following data were extracted: (1) information of researches: first author, year of publication and the country of origin; (2) characteristics of participants: age, sex, sample size, diagnostic criteria and course of disease; (3) interventions: details of sham‐acupuncture; (4) primary and secondary outcomes; (5) information related to the risk of bias (ROB). Corresponding authors were contacted via email to obtain missing data. For multi‐arm RCTs, the eligible comparison or the comparison with an inferior effect size was extracted. If various publications were used to report data from the same trial, we included the study with the most complete or latest data. If the data was displayed in the graph, the WebPlotDigitizer (WebPlotDigitizer—Extract data from plots, images and maps (automeris.io)) was used to extract the data. After cross‐checking, disagreements were settled through consultation with an experienced reviewer (J.L.).

2.6. ROB Assessment

Two researchers (B.J. and J.Z.) evaluated the ROB using the Cochrane risk‐of‐bias tool (version 2.0) for RCTs. There are five domains in ROB2: randomisation process, deviations from intended interventions, missing outcome data, measurement of the outcome and selection of the reported results (Sterne et al. 2019). Each domain is rated as ‘low ROB’, ‘some concerns’, or ‘high ROB’. In case of disagreements, a third investigator (J.L.) was involved.

2.7. Evaluation of the Reporting Quality of Interventions in Clinical Trials of Sham Acupuncture

Sham‐acupuncture reporting guidelines (SHARE) and a checklist are important for an accurate understanding of the specific efficacy of acupuncture and the results of repeated studies (Ma et al. 2023). The SHARE checklist comprises 10 items, including brief name, details of sham acupuncture, treatment regimen of sham acupuncture, the information informed or explained to patients, practitioner information, modifications, communication between practitioner and patient, practitioner adherence and blinding. Two reviewers (B.J. and P.‐W.X.) independently evaluated the included RCTs with the revised SHARE checklist, and any disagreement was arbitrated by consultation with a third reviewer (J.L.).

2.8. Statistical Analysis

Data synthesis was conducted using RevMan (version 5.4) and Stata software (version 12.0). Mean and standard deviations (SDs) of baseline and post‐treatment outcome measures in the sham‐acupuncture group were extracted from each trial. Where SDs within groups were not explicitly reported, they were estimated from the standard error of the mean (SEM) or 95% confidence intervals (CIs) following the procedures detailed in the Cochrane Handbook, Section 6.5.2.2 (Higgins et al. 2021). If outcomes were displayed as medians and interquartile ranges (IQRs), transformed these into means with SDs using the conversion formula proposed by Wan et al. (2014). For continuous data, the weighted mean difference (WMD) and corresponding 95% CI were calculated when the same scale or sleep monitoring system was used, whereas the standardised mean difference (SMD) and 95% CI were computed when different scales or sleep monitoring systems were applied (SE, ST, TST, SOL, WASO). Statistical heterogeneity of included studies was determined by Chi‐square test and I 2 statistics. When homogeneity was presented (p > 0.05 and I 2 < 50%), a fixed effect model was employed for the analysis. Conversely, in the presence of heterogeneity (p ≤ 0.05 and I 2 > 50%), the source of heterogeneity was explored using a random effects model (Borenstein et al. 2010; Zhai and Guyatt 2024). Forest plots were used to present the combined estimates, and values of p < 0.05 were considered statistically significant. Descriptive analyses were performed in case that the data could not be synthesised.

2.9. Subgroup Analysis

Subgroup analyses were conducted based on the following: the presence or absence of skin puncture, the use of acupoints versus non‐acupoints, the type of sham acupuncture employed, the duration of needle retention, the frequency of sham‐acupuncture per week and the duration of the treatment period.

2.10. Sensitivity Analysis

Two sets of sensitivity analyses were undertaken (Higgins et al. 2024). On the one hand, sensitivity analysis was performed by sequentially excluding one study and combining the remaining studies in a meta‐analysis. The influence of each study was assessed by determining whether the revised point estimate lay outside the 95% CI of the original overall effect. This analysis was carried out using Stata (version 12.0). On the other hand, to evaluate the impact of study quality on the results, we excluded studies judged to be at high ROB. The robustness of the findings was determined based on whether the statistical significance of the pooled effect changed—specifically, whether the p‐value transitioned from significant (p < 0.05) to non‐significant (p ≥ 0.05), or vice versa. This analysis was performed using RevMan (version 5.4).

2.11. Publication Bias

The funnel plot, Egger's and Begg's test were used to assess possible publication bias for the primary outcome when studies ≥ 10 with the same outcome were included in the analysis. If publication bias exists, the trim and fill method was used to assess the impact of publication bias on the results (Peters et al. 2007).

2.12. Trail Sequential Analysis (TSA)

We applied TSA for the primary outcome based on studies with a low ROB and several concerns using the TSA software (version 0.9.5.10‐Beta). A random‐effect model was selected with a maximum Type I and II errors of 5% and 20%, respectively (80% power). The cumulative z‐score, monitoring boundary, futility boundary and required information size (RIS) were presented in the TSA graph. The result was reliable when the included sample size reached the RIS or the cumulative Z curve crossed the monitoring and futility boundaries.

3. Results

3.1. Selection and Inclusion of Studies

A total of 4348 articles were retrieved from electronic databases and citation searching. After removing 1039 duplicates, 3221 articles were ineligible and were excluded. By means of reviewing the complete text, 36 eligible studies were finally included. The diagram of the screening process is depicted in Figure 1. The list of excluded records with reasons is provided in Appendix S2.

FIGURE 1.

FIGURE 1

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Flow chart.

3.2. Characteristics of Included Studies

The characteristics of the included trials are indicated in Table 1. A total of 36 trials involving 1129 (control group) patients with PI were included. The sample sizes across the included studies varied significantly from 9 to 52. In various studies, the number of sham acupuncture sessions ranged from 6 to 27, with each session lasting between 15 and 30 min. Of the 36 included studies, sham acupuncture was employed in 29 trials, while sham electroacupuncture was used in 7 trials. The most frequently reported outcome measures across the included studies were PSQI (31 studies), ISI (12 studies), SE (14 studies) and TST (14 studies). The summary of the acupuncture dosage parameters is presented in Appendix S3.

TABLE 1.

Characteristics of included studies.

Author, year Country Sample size Age (year) Sex (male/female) Course of disease (months) Duration of one session (min) The sessions of sham acupuncture Intervention Outcome
Cao et al. (2020) China 36 37.30 ± 15.10 15/21 13.20 ± 3.60 30 12 Sham acupuncture SE, SA, TST
Cui et al. (2021) China 18 50.50 (29, 58) 4/14 NA 30 6 Sham acupuncture PSQI, ISI
Feng et al. (2020) China 45 47 ± 10 16/29 14.30 ± 6.20 30 20 Sham acupuncture ISI, SE, TST, SOL, WASO, N1, N2, N3, REM
Gou (2015) China 30 37 ± 14 6/24 13.20 ± 3.60 30 12 Sham acupuncture ISI, SE, SA, TST
Huangfu (2019) China 12 29.91 ± 10.76 2/9 NA 30 20 Sham acupuncture PSQI
Huo et al. (2023) China 30 46 ± 8 16/14 36 (12, 48) 30 12 Sham acupuncture PSQI, FS‐14
Jin et al. (2020) China 40 42.60 ± 13.40 11/29 14.20 ± 4.20 30 9 Sham acupuncture ISI, SE, TST, SOL
Li (2010) China 30 32.20 ± 1.80 11/19 18 ± 5.10 30 10 Sham acupuncture PSQI
Liu (2017) China 36 45.66 ± 11.02 11/27 NA 20 10 Sham acupuncture PSQI, ISI, SE, TST, SOL
Tan (2022) China 16 44.19 ± 18.19 5/11 12 (8.50, 18) 20 12 Sham acupuncture PSQI
Wang, Qin, et al. (2021) China 29 69 ± 5 11/18 19.70 ± 5.70 30 12 Sham electroacupuncture PSQI
Wu et al. (2021) China 32 46.22 ± 11.91 11/21 33.60 ± 39.84 30 12 Sham electroacupuncture PSQI, FS‐14
Wu et al. (2020) China 41 45.56 ± 13.64 5/36 60 (80.50) 30 12 Sham acupuncture PSQI
Xi et al. (2021) China 29 41 ± 12 13/16 68.40 ± 56.40 30 12 Sham electroacupuncture PSQI
Yang et al. (2023) China 35 52 ± 4 NA 10.80 ± 3.20 30 10 Sham acupuncture PSQI, SE, TST, SOL, WASO, N1, N2, N3, REM
Yang (2017) China 37 54.50 (40, 60) NA NA 30 10 Sham acupuncture PSQI, ISI, FS‐14
Zhao (2020) China 27 45.59 ± 12.65 10/17 34.80 ± 42.6 30 12 Sham electroacupuncture PSQI, FS‐14
Zhao, Xu, et al. (2019) China 32 39.31 ± 10.88 15/17 4 ± 1.50 30 24 Sham acupuncture PSQI
Zhao, Kim, et al. (2019) China 25 49.64 ± 3.55 NA 12.15 ± 5.71 15 24 Sham acupuncture PSQI, SE, SA, TST
Zhao et al. (2018) China 30 38.40 ± 10.80 14/16 4.70 ± 1.30 30 24 Sham acupuncture PSQI
Zuppa et al. (2015) Brazil 24 65.75 ± 3.80 5/19 NA 25 10 Sham acupuncture PSQI
Lee et al. (2020) Korea 52 52 (49.52, 54.58) 9/43 72.35 (53.59, 91.10) 30 10 Sham electroacupuncture PSQI, ISI, SE, TST, SOL, WASO
Fu et al. (2017) China 37 52.50 ± 5.90 NA NA 20 10 Sham acupuncture PSQI, ISI, SE, TST, SOL, WASO, N1, N2, N3, REM
Wang, Xu, et al. (2021) China 41 58 (25, 73) 10/31 120 (6, 480) 20 10 Sham acupuncture PSQI, ISI, FS‐14, SE, TST, SOL, WASO, N1, N2, N3, REM
Hachul et al. (2013) Brazil 9 NA NA NA 30 10 Sham acupuncture PSQI, SE, N3, REM
Leung (2016) China 30 33.27 ± 10.90 13/17 7.37 ± 7.07 30 10 Sham acupuncture PSQI
Foroughinia et al. (2020) Iran 29 30.20 ± 3.40 0/29 NA 30 10 Sham acupuncture PSQI
Li et al. (2020) China 42 53.07 (3.81) NA 40.21 (16, 60) 30 18 Sham electroacupuncture PSQI, ISI, SE, SA, TST, WASO
Yin et al. (2017) China 36 37.30 ± 15.10 15/21 NA 30 12 Sham acupuncture ISI, SE, SA, TST
Chen et al. (2023) China 24 40 (20) 10/14 NA 30 12 Sham acupuncture PSQI, TST, WASO
Zhang et al. (2020) China 48 39.20 ± 13.80 21/27 21.60 ± 16.90 30 10 Sham acupuncture PSQI
Zhang, Deng, et al. (2023) China 46 39.41 ± 13.93 16/30 NA 30 10 Sham acupuncture PSQI
Yeung et al. (2009) China 30 47.80 ± 8.60 6/24 129.60 (200.40) 30 9 Sham electroacupuncture PSQI, ISI, SE, TST, SOL, WASO
Zhang et al. (2025) China 22 36 (16) 10/12 2 (3.50) 30 12 Sham acupuncture PSQI, FS‐14, SE, TST
Peng et al. (2024) China 19 30.33 ± 9.33 4/15 41.14 ± 34.63 30 20 Sham acupuncture PSQI
Jiang et al. (2024) China 30 37.50 ± 1.80 11/19 55.68 ± 62.64 30 20 Sham acupuncture PSQI, SE, TST, WASO
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Note: Values are presented as mean ± standard deviation, median (interquartile range) or number (%).

Abbreviations: FS‐14, Fatigue Scale‐14; ISI, Insomnia Severity Index; N, non‐rapid eye movement; PSQI, Pittsburgh sleep quality index; REM, rapid eye movement; SA, sleep awakening; SE, sleep efficiency; SOL, sleep inset latency; TST, total sleep time; WASO, wake after sleep onset.

3.3. ROB Assessment

The plot of ROB2 for individual study is presented in Figure 2, and the proportions of included studies are depicted in Figure 3. In the domain of the randomisation process, 8 studies (Li 2010; Zhao, Kim, et al. 2019; Zuppa et al. 2015; Hachul et al. 2013; Leung 2016; Yeung et al. 2009; Zhang et al. 2025; Peng et al. 2024) were categorised as some concerns due to no details of randomisation or allocation concealment, while the remaining studies were classified as low risk. Regarding deviations from intended interventions, 3 studies (Cao et al. 2020; Cui et al. 2021; Li 2010) had some concerns because of no information on deviation from intended interventions, and the rest of the studies were considered as low risk. In terms of missing outcome data, 2 studies (Gou 2015; Foroughinia et al. 2020) had high risk for high rates of drop‐outs or lost to follow‐up, and the rest were low risk. With regard to measurement of the outcome, 12 studies (Cui et al. 2021; Gou 2015; Li 2010; Tan 2022; Wu et al. 2020, 2021; Zhao, Xu, et al. 2019; Zhao, Kim, et al. 2019; Zhao et al. 2018; Zuppa et al. 2015; Leung 2016; Zhang et al. 2025) did not report the blindness of outcome assessors and were rated as high risk. The rest of the studies were evaluated as low risk. Considering selection of the reported result, 15 studies (Cao et al. 2020; Cui et al. 2021; Jin et al. 2020; Li 2010; Liu 2017; Tan 2022; Wu et al. 2020, 2021; Yang et al. 2023; Zhao, Xu, et al. 2019; Zhao, Kim, et al. 2019; Zhao et al. 2018; Zuppa et al. 2015; Hachul et al. 2013; Leung 2016) had some concerns because study protocols were not always available, and the rest had low risk.

FIGURE 2.

FIGURE 2

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Results of ROB2 assessment. The plot of RoB2.0 for each included study.

FIGURE 3.

FIGURE 3

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Results of ROB2 assessment. Proportions of individual studies for each domain.

In summary, the overall ROB in 13 studies were considered as high risk, 7 studies were categorised as some concerns and the remaining were considered as low risk.

3.4. The Reporting Quality of Interventions in Clinical Trials of Sham Acupuncture

The SHARE checklist is shown in Appendix S4. All studies reported the brief name, needle retention time, number, frequency and duration of treatment sessions. A total of 31 trials (Cao et al. 2020; Cui et al. 2021; Feng et al. 2020; Huangfu 2019; Huo et al. 2023; Jin et al. 2020; Li 2010; Liu 2017; Tan 2022; Wang, Qin, et al. 2021; Wu et al. 2020; Xi et al. 2021; Yang et al. 2023; Yang 2017; Zhao 2020; Zhao, Xu, et al. 2019; Zhao, Kim, et al. 2019; Zhao et al. 2018; Zuppa et al. 2015; Lee et al. 2020; Fu et al. 2017; Wang, Xu, et al. 2021; Hachul et al. 2013; Leung 2016; Foroughinia et al. 2020; Li et al. 2020; Chen et al. 2023; Zhang et al. 2020, 2025; Yeung et al. 2009; Jiang et al. 2024) described the needle device employed. One studies (Hachul et al. 2013) did not describe the names of points used and needle insertion methods. Twenty studies (Yin et al. 2017; Cao et al. 2020; Cui et al. 2021; Feng et al. 2020; Gou 2015; Huo et al. 2023; Li 2010; Liu 2017; Tan 2022; Wang, Qin, et al. 2021; Xi et al. 2021; Yang et al. 2023; Yang 2017; Zhao 2020; Zhao, Kim, et al. 2019; Zuppa et al. 2015; Fu et al. 2017; Wang, Xu, et al. 2021; Leung 2016; Zhang, Deng, et al. 2023) provided information on the position taken by patients during treatment. More than half of the trials described the depth, angle and direction of needle insertion. Among included studies, 24 studies (Yin et al. 2017; Cui et al. 2021; Feng et al. 2020; Huangfu 2019; Huo et al. 2023; Li 2010; Liu 2017; Tan 2022; Wu et al. 2020, 2021; Xi et al. 2021; Yang et al. 2023; Yang 2017; Zhao 2020; Lee et al. 2020; Wang, Xu, et al. 2021; Leung 2016; Foroughinia et al. 2020; Li et al. 2020; Chen et al. 2023; Zhang et al. 2020; Zhang, Deng, et al. 2023; Yeung et al. 2009; Peng et al. 2024) reported whether de qi or other procedures were performed. Practitioner information was reported in 15 studies (Feng et al. 2020; Huangfu 2019; Huo et al. 2023; Jin et al. 2020; Liu 2017; Tan 2022; Wu et al. 2021; Xi et al. 2021; Yang et al. 2023; Yang 2017; Zhao 2020; Wang, Xu, et al. 2021; Zhang et al. 2025; Peng et al. 2024; Jiang et al. 2024). Except for 4 trials (Cao et al. 2020; Gou 2015; Tan 2022; Lee et al. 2020), the rest of the trials did not specify the communication between practitioner and patient. In total, 11 studies (Yin et al. 2017; Cao et al. 2020; Gou 2015; Huangfu 2019; Liu 2017; Wang, Qin, et al. 2021; Xi et al. 2021; Yang 2017; Wang, Xu, et al. 2021; Hachul et al. 2013; Leung 2016) elucidated methods to enhance the success rate of blinding procedures, and two studies (Tan 2022; Lee et al. 2020) conducted evaluation of blinding.

3.5. Results of the Meta‐Analysis

3.5.1. Primary Outcome

A total of 31 trials reported the changes of PSQI. The results demonstrated that sham acupuncture was beneficial for the improvement of PSQI (WMD = 1.38, 95% CI 0.90–1.86, p < 0.00001, I 2 = 76%; Figure 4). The sensitivity analysis showed that the results were stable (Appendix S5).

FIGURE 4.

FIGURE 4

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Forest plot of the effect of sham acupuncture on PSQI in patients with PI.

3.5.1.1. Subgroup Analysis

As depicted in Table 2, there were no differences in subgroups of skin penetration, needling position, needle retention duration and treatment period. Subgroup analysis indicated that the types of sham acupuncture were a significant contributor to the heterogeneity.

TABLE 2.

Subgroup analysis of PSQI outcome.

Subgroup Number of studies Patients (B, before intervention/A, after intervention) Overall effect Heterogeneity
Effect size (95% CI) p I 2 p
1.1 Subgroup analysis by skin penetration
Yes 20 518/516 1.33 [0.68, 1.99] < 0.0001 80% < 0.00001
No 11 417/413 1.45 [0.78, 2.12] < 0.0001 65% 0.002
Subgroup differences 0.81
1.2 Subgroup analysis by needling position
Acupoints 11 380/375 1.24 [0.66, 1.83] < 0.0001 48% 0.04
Sham acupoints 20 555/554 1.42 [0.75, 2.09] < 0.0001 82% < 0.00001
Subgroup differences 0.70
1.3 Subgroup analysis by type of sham acupuncture
Acupoints with skin penetration 2 45/44 2.05 [0.70, 3.39] 0.003 0% 0.63
Acupoints without skin penetration 9 335/331 1.13 [0.49, 1.76] 0.0005 53% 0.03
Non‐acupoints with skin penetration 18 473/472 1.26 [0.57, 1.96] 0.0004 82% < 0.00001
Non‐acupoints without skin penetration 2 82/82 2.77 [1.83, 3.71] < 0.00001 0% 0.74
Subgroup differences 0.03
1.4 Subgroup analysis by needle retention duration
< 20 min 3 78/78 1.53 [0.70, 2.36] 0.0003 27% 0.26
≥ 20 min 28 857/851 1.38 [0.85, 1.90] < 0.00001 78% < 0.00001
Subgroup differences 0.76
1.5 Subgroup analysis by treatment period
< 4 weeks 10 351/347 1.54 [0.89, 2.19] < 0.00001 67% 0.001
≥ 4 weeks 21 584/582 1.29 [0.64, 1.95] 0.0001 79% < 0.00001
Subgroup differences 0.60
1.6 Subgroup analysis by treatment frequency
< 3 times a week 5 151/151 1.01 [−1.17, 3.20] 0.36 94% < 0.00001
≥ 3 times a week 25 742/736 1.43 [1.09, 1.78] < 0.00001 39% 0.02
Subgroup differences 0.71
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3.5.1.2. Publication Bias

The funnel plot seemed asymmetrical, and the result of Begg's test (p = 0.415) and Egger's test (p = 0.018) indicated publication bias existed (Figure 5). The results of the trim‐and‐fill method estimated the number of missing studies to be 10. The results remained consistent after the inclusion of the 10 additional studies, which suggested that the findings were robust.

FIGURE 5.

FIGURE 5

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Funnel plot of the effect of sham acupuncture on PSQI in patients with PI.

3.5.2. Secondary Outcomes

3.5.2.1. ISI

A total of 12 trials reported the changes of ISI. The results demonstrated that sham acupuncture was effective to reduce the scores of ISI (WMD = 2.58, 95% CI 1.46–3.69, p < 0.00001, I 2 = 80%; Figure 6). The sensitivity analysis showed that the results were robust (Appendix S6).

FIGURE 6.

FIGURE 6

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Forest plot of the effect of sham acupuncture on ISI in patients with PI.

3.5.2.2. FS‐14

Six trials documented the changes of FS‐14. The results demonstrated that sham acupuncture was beneficial for reduction of FS‐14 (SMD = 0.77, 95% CI 0.03–1.51, p = 0.04, I 2 = 91%; Figure 7).

FIGURE 7.

FIGURE 7

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Forest plot of the effect of sham acupuncture on FS‐14 in patients with PI.

3.5.2.3. SE

A total of 14 trials reported the changes of SE. The results showed that there was no difference in SE between patients with PI before and after the sham acupuncture intervention (SMD = −0.14, 95% CI −0.32 to 0.04, p = 0.12, I 2 = 47%; Figure 8). The results of the sensitivity analysis showed that the results were stable (Appendix S7).

FIGURE 8.

FIGURE 8

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Forest plot of the effect of sham acupuncture on SE in patients with PI.

3.5.2.4. SA

The pooled results from 5 trials demonstrated that sham acupuncture was not effective to reduce the scores of SA (WMD = 1.01, 95% CI −0.31 to 2.33, p = 0.13, I 2 = 4%; Figure 9).

FIGURE 9.

FIGURE 9

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Forest plot of the effect of sham acupuncture on SA in patients with PI.

3.5.2.5. TST

The synthesised results based on 14 studies demonstrated that sham acupuncture was not beneficial for reduction of TST scores (SMD = 0.15, 95% CI −0.09 to 0.40, p = 0.23, I 2 = 72%; Figure 10). The results of the sensitivity analysis showed that the results did not change (Appendix S8).

FIGURE 10.

FIGURE 10

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Forest plot of the effect of sham acupuncture on TST in patients with PI.

3.5.2.6. SOL

The results demonstrated that sham acupuncture could not reduce the scores of SOL (SMD = −0.31, 95% CI −0.97 to 0.35, p = 0.35, I 2 = 90%; Figure 11).

FIGURE 11.

FIGURE 11

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Forest plot of the effect of sham acupuncture on SOL in patients with PI.

3.5.2.7. WASO

A total of 6 trials reported the changes of WASO. The results revealed that sham acupuncture could not decrease the scores of WASO (SMD = 0.03, 95% CI −0.16 to 0.23, p = 0.75, I 2 = 0%; Figure 12).

FIGURE 12.

FIGURE 12

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Forest plot of the effect of sham acupuncture on WASO in patients with PI.

3.5.2.8. N1

The results discovered that sham acupuncture had no influence on N1 (WMD = 0.81, 95% CI −0.44 to 2.07, p = 0.21, I 2 = 39%; Figure 13).

FIGURE 13.

FIGURE 13

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Forest plot of the effect of sham acupuncture on N1 in patients with PI.

3.5.2.9. N2

The pooled results showed that sham acupuncture could not change N2 (WMD = 0.75, 95% CI −1.10 to 2.60, p = 0.43, I 2 = 0%; Figure 14).

FIGURE 14.

FIGURE 14

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Forest plot of the effect of sham acupuncture on N2 in patients with PI.

3.5.2.10. N3

A total of 4 trials reported the changes of N3. The results demonstrated that sham acupuncture had no impact on N3 (WMD = −0.26, 95% CI −1.42 to 0.91, p = 0.67, I 2 = 0%; Figure 15).

FIGURE 15.

FIGURE 15

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Forest plot of the effect of sham acupuncture on N3 in patients with PI.

3.5.2.11. REM

The results revealed that sham acupuncture was not beneficial for REM (WMD = −0.87, 95% CI −4.27 to 2.53, p = 0.62, I 2 = 86%; Figure 16).

FIGURE 16.

FIGURE 16

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Forest plot of the effect of sham acupuncture on REM in patients with PI.

3.6. TSA

Cumulative Z curves of the primary outcome crossed the monitoring and futility boundary. Moreover, the included sample sizes reached the RIS. The graphs of TSA are provided in Appendix S9.

4. Discussion

Pooled results from 36 RCTs revealed that the application of sham acupuncture could significantly reduce scores of the PSQI, ISI and FS‐14, which indicated that sham acupuncture was effective to improve sleep quality and alleviate sleep‐related dysfunction. Nevertheless, no significant alterations were observed in the polysomnographic and actigraphy indices after sham acupuncture treatment. Subgroup analysis demonstrated that the reduction of PSQI scores varied from different types of sham acupuncture in patients with PI.

Minimal clinically important difference (MCID) serves as a pivotal metric for assessing the clinical significance of therapeutic outcomes (Chan 2013). Qin et al. (2024) revealed that the MCID for the PSQI in individuals with insomnia ranged from 2.5 to 2.7, and the MCID of ISI was 4. In the present study, the placebo effect of the sham acupuncture was determined based on the MD and 95% CI of the PSQI scores from the baseline to after treatment. The WMD of sham acupuncture for the PSQI in individuals with insomnia was 1.38, and the corresponding WMD for the ISI was found to be 2.58. These results indicated that sham acupuncture could alleviate subjective insomnia symptoms to some extent, but had no clinical significance. Xie, Xiong, et al. (2023) reported that beliefs about the efficacy of treatment could significantly improve symptoms due to psychological effects. Belief itself is a psychological suggestion; patients with belief prefer to have psychological expectations and confidence in treatment. The positive psychological state is associated with relief of the tension and anxiety in patients with insomnia, and is beneficial for the improvement of sleep (Lu et al. 2023). Conversely, no substantial alterations were detected in the objective sleep parameter assessments. These results indicated that the placebo effect of sham acupuncture was associated with the subjective perception of relief, without alterations of measurable indicators. Lundeberg et al. (2007) revealed that sham acupuncture could activate patients' expectations and beliefs, and modulate the activity of the reward system. Any form of skin irritation (including non‐penetrating false needles) can activate the C fibres that connect to the mechanical receptors in the skin, thereby activating the insula and limbic system (the core components of the reward system), triggering a pleasant and reward‐related response. Peng et al. (2024) found increased functional connectivity between left dorsal‐lateral prefrontal cortex and left anterior insula, and right supplementary motor area and medial hypothalamus in patients with insomnia treated with sham acupuncture. Evidence indicated that the hypothalamus played a crucial role in reward mechanisms (Noritake et al. 2023; Soden et al. 2023). Soden et al. (2023) found that neurons in the lateral hypothalamus were capable of releasing neurotensin and forming synaptic connections with dopaminergic neurons, thereby regulating reward mechanisms. Zang et al. (2023) concluded that sham acupuncture induced changes of the left superior frontal gyrus, left inferior frontal gyrus and right inferior frontal gyrus in patients with PI. However, the mechanisms on the placebo effect of sham acupuncture remain unclear. Multidisciplinary methods should be used to reveal the complex mechanism of the placebo effect of sham acupuncture.

In the present study, sleep monitoring techniques such as polysomnographic and actigraphy were adopted in 15 of the 36 studies. Different from subjective scales, sleep monitoring could reduce subjective bias and improve the reliability of the study. We pooled data of sleep monitoring indicators including SE, SA, TST, SOL, WASO, N1, N2, N3, REM and the results showed that sham acupuncture had no beneficial effect. Future studies are encouraged to incorporate sleep monitoring techniques to mitigate the impact of unblinding on the results, thereby enhancing the reliability of the findings.

Our review incorporated trials that utilised diverse sham acupuncture techniques, representing a potential source of clinical and methodological heterogeneity. These interventions can be classified into four main categories. (1) Acupoints without skin penetration: Patients with PI received non‐insertive needling at designated acupoints using a Park device‐supported sham needle. This device features a retractable shaft and a blunt tip, preventing actual skin penetration (To and Alexander 2015). (2) Non‐acupoints with skin penetration: Patients with PI underwent shallow or deep needling at non‐acupoint locations. (3) Acupoints with skin penetration: Patients received superficial needling at specific acupoints without manual manipulation. (4) Non‐acupoints without skin penetration: Non‐insertive sham needling was applied at non‐acupoint sites using the Park device. The placebo effect produced by sham acupuncture types were ranged as followed: acupoints without skin penetration < non‐acupoints with skin penetration < acupoints with skin penetration < non‐acupoints without skin penetration. Similarly Xiong et al. (2023) revealed that the therapeutic efficacy of sham acupuncture for the management of low back pain varied from the types of sham acupuncture, and sham acupuncture on acupoints without skin penetration had the smallest placebo effect. Variations in sham acupuncture methodology may influence study outcomes through three key mechanisms. First, certain sham acupuncture techniques may exhibit greater physiological inertness than others. For instance, non‐penetrating devices are likely to produce minimal specific physiological effects, whereas superficial needling at non‐acupoints may still induce minor, non‐specific neuromodulatory responses. Second, differences in the magnitude of placebo effects associated with sham acupuncture may be attributed to variability in patient expectations. The expected therapeutic value of acupuncture has been shown to significantly influence clinical outcomes (Yang et al. 2022). In a study by Xu (2023) investigating press needle therapy for functional constipation, patients with higher expectation levels demonstrated superior outcomes compared to those with lower expectations, suggesting a positive correlation between expectation levels and treatment efficacy. Similarly, Gollub et al. (2018) conducted a RCT examining verum and sham electroacupuncture in patients with knee osteoarthritis. Through verbal suggestion and conditioning procedures applied to both groups, expectations for analgesic effects were enhanced, resulting in no significant difference in subjective pain scores between verum and sham elecroacupuncture. This further supports that elevated treatment expectations can amplify the placebo effects of sham acupuncture. However, none of the studies included in our analysis assessed acupuncture‐related expectations among insomnia patients. Consequently, the influence of patient expectations on placebo effects in primary insomnia remains unclear and warrants further investigation. Third, the integrity of blinding is crucial for assessing placebo effects. Due to the technical particularity of sham acupuncture procedures, practitioners cannot be blinded to treatment allocation. In addition to lack of blinding, potential psychological expectations from patients and outcome assessors may lead to either overestimation or underestimation of treatment effects (Huneke et al. 2025; Long et al. 2024). Among 36 included studies, two studies conducted blinding test to assess the implementation of blinding and reported successful blinding. Blinding test are recommended for the RCT with sham acupuncture as a comparison.

The dosage parameters of sham acupuncture are important moderators of its therapeutic outcomes. Lee et al. (2022) noted that the quality of reporting on sham acupuncture procedures in clinical trials remains relatively low. To address this issue, we applied the SHARE checklist to evaluate the methodological rigour of sham acupuncture protocols and incorporated dose‐related parameters into both statistical and subgroup analyses. Our subgroup analyses revealed that the smallest placebo effect was associated with acupoint stimulation without skin penetration, while the largest effect was observed in the non‐acupoint group without skin penetration. However, these findings are not entirely consistent with existing literature. For instance, Wan et al. (2025) reported the lowest placebo effect in non‐penetrating sham acupuncture for chronic pain. A study on migraine identified treatment frequency as a significant predictor of placebo response, this factor appeared to have limited influence in our results (Sun et al. 2023). To reduce heterogeneity and enhance the validity of future trials, it is essential to standardise the application of sham acupuncture and clarify its suitability as a placebo control. We recommend adopting minimalistic sham acupuncture methods that induce the smallest placebo effect as the control intervention. Such an approach would help isolate the specific effects of verum acupuncture and improve consistency across sham acupuncture protocols.

There were several limitations in our study. First, high heterogeneity was detected among the included studies and the results should be interpreted with caution. Second, we included studies published in both Chinese and English, and language bias might exist. Third, some of the included studies were of limited methodological rigour. In several studies, the lack of blinding among assessors could compromise the reliability of the findings. Fourth, the lack of a well‐established MCID for the FS‐14 scale is a notable constraint. Although we observed a statistically significant improvement in FS‐14 scores, the absence of a validated MCID threshold renders it difficult to definitively assess its clinical magnitude and implications for patient experience.

5. Conclusion

Overall, sham acupuncture had a certain placebo effect in clinical trials of PI. The placebo effect varied among different types of sham acupuncture. Due to the limitations of RCT design, more RCTs are needed in the future to validate the placebo effect of sham acupuncture for insomnia.

Author Contributions

Bo Jiang: conceptualization, investigation, writing – original draft, data curation. Yi‐Nan Wang: writing – review and editing, methodology. Jun Zhang: data curation, formal analysis. Hong‐Ru Li: software. Pei‐Wen Xue: data curation. Juan Li: writing – review and editing, supervision. Rong‐Jiang Jin: writing – review and editing, supervision.

Funding

This work was supported by Special Scientific and Technological Research Project of Sichuan Provincial Administration of Traditional Chinese Medicine, 2024MS310.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Data S1: jsr70280‐sup‐0001‐Appendix.zip.

JSR-35-e70280-s001.zip (8.5MB, zip)

Contributor Information

Juan Li, Email: 785939016@qq.com.

Rong‐Jiang Jin, Email: cdzyydxjrj@126.com.

Data Availability Statement

The original contributions presented in the study are included in the article Supporting Information. Further inquiries can be directed to the corresponding authors.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Data S1: jsr70280‐sup‐0001‐Appendix.zip.

JSR-35-e70280-s001.zip (8.5MB, zip)

Data Availability Statement

The original contributions presented in the study are included in the article Supporting Information. Further inquiries can be directed to the corresponding authors.

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