Placebo effect was influenced by publication year in three-armed acupuncture trials

Acupuncture, autonomic nervous system and biophysical origin of acupuncture system

“…creasing of its effect (placebo) during time. But, We et al 50 gave evidence that there is an increase of sham acupuncture effect as its date of publication is closer to the present time. After reconsidering all possible factors they think that it is probably due to method of article selection for publishing in journals.…”

Time Course of Placebo Effect of Acupuncture on Pain: A Systematic Review

“…Among 7078 citations (MEDLINE 546, SCOPUS 5804, and the Cochrane Registered Trials 728) in a new search, we identified 12 potentially eligible trials ( Figure 1 ). After a screening of 44 trials including 32 trials that were analyzed in previous studies [ 6 , 7 ], we further excluded 29 trials: 19 reported on non-pain-related diseases, and ten were conducted for one day. In total, 15 trials that met the selection criteria were analyzed [ 15 – 29 ].…”

“…Previously, 32 three-armed randomized acupuncture trials were identified using MEDLINE, CINAHL, EMBASE, and the Cochrane Registered Trials from their launch through October 2009 [ 6 , 7 ]. From October 2009 to December 2011, the first author searched MEDLINE, SCOPUS, and the Cochrane Registered Trials using the same terms “acupuncture,” “electroacupuncture,” and “electro-acupuncture.” Then the first author selected randomized clinical trials that met the following conditions: (1) reported data on pain, (2) included an acupuncture group where dry needles were inserted in traditional or painful points, (3) included a sham group where an intervention was considered a sham or a placebo acupuncture in the text, (4) included a no-treatment group where no treatment was applied, and (5) compared the above three groups under identical conditions in one trial.…”

“…Nevertheless, it has been reported that all types of sham acupuncture may not be physiologically inert [ 3 – 5 ]. Moreover, according to a series of recent studies [ 6 , 7 ], there is a high possibility of publication bias, where trials with negative results in a treatment group would be less likely to be published, in the three-armed randomized trials including sham and no-treatment groups. When the bias was considered, the magnitude of the placebo effect was calculated to be large [ 6 ].…”

“…However, all these findings [ 3 – 7 ] should be interpreted with caution because they were based on the data measured at one time point, as specified by authors of trials. To date, it has not been studied how the placebo effect changes over time.…”