Placebo response varies between different types of sham acupuncture: A randomized double-blind trial in neck pain patients

Neck pain is an extremely common condition that affects approximately 70% of people at some point in their lives, with many experiencing chronic or recurrent episodes. Despite its high prevalence, available conventional treatments are often ineffective for many individuals. Acupuncture has emerged as a promising therapeutic option, working through the release of natural body substances that fight pain (such as endogenous opioids) and modulating brain regions associated with pain perception. Previous studies have demonstrated that acupuncture is particularly effective for musculoskeletal pain in the upper body, including neck pain.

However, acupuncture remains a controversial treatment for neck pain. One of the main difficulties in scientific research on this therapy is related to the different types of "sham" acupuncture used as control in studies. These controls are necessary to determine whether the observed benefits are really due to true acupuncture or just to the placebo effect. The problem is that there are several ways to apply sham acupuncture, including superficial needling at correct points, deep needling at incorrect points, superficial needling at incorrect points, or even the use of needles that do not penetrate the skin.

Each type of control can produce different levels of placebo effect, making it difficult to evaluate the true efficacy of acupuncture.

The objective of this study was to compare the specific and non-specific effects of electroacupuncture with four different types of sham acupuncture in patients with neck pain. Researchers conducted a controlled, double-blind, randomized study in which 175 patients with neck pain for at least three months were randomly divided into five groups. The first group received true electroacupuncture (deep needling at correct points with electrical stimulation), while the other four groups received different types of sham acupuncture: superficial needling at correct points, deep needling at incorrect points, superficial needling at incorrect points, and application of needles without skin penetration. All participants received ten treatment sessions over three weeks, with each session lasting approximately 30 minutes.

To evaluate the results, researchers used several measurement scales. The primary one was the Northwick Park Neck Pain Questionnaire (NPQ), which evaluates not only pain intensity but also how it affects the patient's daily activities, sleep, and quality of life. As secondary measures, the Short-Form McGill Pain Questionnaire, a visual analog pain scale (VAS), and an objective test to measure pain threshold were used. Patients were evaluated at baseline, after five sessions, after ten sessions, and three months after the end of treatment.

The results revealed surprising findings about how different types of sham acupuncture produce distinct effects. All groups, except for superficial needling at incorrect points, showed significant improvements on all pain measures evaluated. Electroacupuncture demonstrated superiority only when compared with three of the four types of control: superficial needling at correct points, superficial needling at incorrect points, and needles without penetration. Even more interesting was the discovery that deep needling at incorrect points produced analgesic effects very similar to those of true electroacupuncture, with no statistically significant differences between them.

A particularly intriguing observation was that superficial needling at incorrect points produced even less placebo effect than needles without skin penetration. This suggests that the combination of superficial penetration with incorrect localization may be less effective than simply simulating the sensation of the needle without penetrating the skin. True electroacupuncture achieved a clinically significant reduction of 52% on the NPQ scale after the ten treatment sessions.

The clinical implications of this study are substantial both for patients and for health professionals. For patients, the results suggest that electroacupuncture may be an effective option for the treatment of chronic neck pain, offering clinically significant improvements that are maintained over time. However, the study also reveals that part of the observed benefits may be related to non-specific effects of the treatment, including the placebo effect and the benefits of being treated itself.

For health professionals, this work provides important information on how to interpret scientific studies of acupuncture. The finding that different types of control produce widely varying placebo effects means that the apparent efficacy of acupuncture may depend significantly on the type of control used in the study. This may explain why some studies show large benefits of acupuncture while others show minimal benefits. The study also demonstrates that even techniques considered as "placebo" can produce real therapeutic effects, especially when they involve needle penetration into deep tissues.

The work also reveals that different methods of pain assessment may be more or less sensitive in detecting the effects of acupuncture. The NPQ and VAS scales proved more sensitive in identifying differences between electroacupuncture and controls than other measures used. This has important implications for how future studies should be conducted and how results should be interpreted.

Despite its important findings, the study presents some limitations that should be considered. The main limitation was the difficulty in keeping participants "blinded" as to the type of treatment received. Approximately 79% of patients who received true electroacupuncture were able to correctly identify that they were receiving real treatment, possibly due to the characteristic sensations of electrical stimulation and needle manipulation. This is a common limitation in studies of acupuncture and other therapies that involve physical stimulation.

In addition, the study was conducted at a single medical center in China, which may limit the applicability of the results to other populations and cultural contexts.

In conclusion, this study provides important evidence on the efficacy of electroacupuncture for neck pain and reveals the complexity of placebo effects in different types of acupuncture controls. The results suggest that electroacupuncture may be a valuable therapeutic option for patients with chronic neck pain, but they also highlight the importance of understanding that part of the benefits may be related to non-specific effects. For patients considering acupuncture as a treatment, these findings offer hope that the therapy may provide significant pain relief. For the scientific community, the work emphasizes the need for caution in interpreting acupuncture studies and the importance of considering the type of control used when evaluating treatment efficacy.

The study contributes to a better understanding of the mechanisms underlying acupuncture and may guide the development of