Non-penetrating placebo needles were introduced to provide rigorous sham controls in randomized controlled trials of acupuncture, yet accumulating evidence indicates that they are neither fully physiologically inert nor reliably indistinguishable from verum acupuncture. This review synthesizes conceptual and empirical work on placebo mechanisms, placebo controls, and contextual effects in acupuncture in order to clarify the status of non-penetrating placebo needles and their contribution to the “efficacy paradox” in acupuncture trials. We conducted a narrative review with a purposive search strategy that used our randomized trials of acupuncture with non‑penetrating placebo needles as index studies and was complemented by targeted reading of key clinical and experimental research on placebo and contextual effects in acupuncture. Current placebo needles frequently function as active placebos: they can induce deqi-like sensations, autonomic responses, and robust expectations of benefit, while only imperfectly maintaining blinding. Consequently, sham acupuncture often produces substantial improvements over no treatment or usual care, yielding modest differences between real and sham acupuncture despite clinically meaningful benefits in both groups. At the same time, expectations, learning, and contextual features—especially the patient–practitioner relationship, communication style, and the broader clinical environment—emerge as major biobehavioral determinants of outcome. Taken together, these observations suggest that non‑penetrating placebo needles do not behave as inert placebos but as active comparators that capture powerful contextual and psychobiological influences on clinical responses. Recognizing this dual role is important for interpreting sham‑controlled acupuncture trials and for understanding the contribution of placebo mechanisms to outcomes in acupuncture research and practice.
Lee et al. (Wed,) studied this question.