Acupuncture therapy is effective in the treatment of quite a lot of clinical conditions. Accumulating evidence demonstrates that acupuncture therapy not only has specific therapeutic effects, but also in a large part has non-specific effects such as the patient's and/or acupuncture practitioner's "unity of form and spirit", "treatment experience and environment" and "expectations and trust", etc. In the present article, we make a review about progresses of recent researches on the non-specific effect of acupuncture therapy and its influencing factors from 1) placebo acupuncture, 2) expectancy effect, 3) Hawthorne effect, and 4) Pygmalion effect. The placebo acupuncture intervention may enhance the therapeutic effect by triggering the cutaneous somatosensory afferents, brainstem, hypothalamus, limbic system, etc. to produce cognitive and emotional responses. The patient's expectancy and belief about acupuncture analgesia are associated with activities of the spino-thalamo-cortical pathway, cingulate gyrus, endogenous opioid system, emotional and reward circuits, etc. Regarding the Hawthorne effect and Pygmalion effect, it is supposed that the patients' behavioral tendency changes and higher expectations for acupuncture treatment may produce a positive impact on the outcomes of treatment. In-depth exploration of the influencing factors and the therapeutic targets of acupuncture treatment will further improve clinical effect, and serve the patients better.
Keywords: Acupuncture; Influencing factors; Mechanisms; Non-specific effects; Placebo effect.