Efficacy of cupping therapy on pain outcomes: an evidence-mapping study

This evidence-mapping study represents a comprehensive and systematic analysis of the efficacy of cupping therapy in the treatment of pain-related conditions. The researchers conducted a review of 14 meta-analyses that included studies on five distinct types of painful conditions, encompassing a total of 12,588 participants. Cupping therapy, a millennia-old healing technique that involves the application of cups to the skin to create negative pressure, has gained growing recognition as a complementary therapy in chronic pain management. The main objective was to provide a complete overview of the available scientific evidence on this therapeutic modality, evaluating both its efficacy and the quality of the studies that support it.

The methodology employed followed rigorous standards of systematic review, with searches in four main medical databases: PubMed, Cochrane Library, Embase, and Web of Science. The inclusion criteria focused specifically on meta-analyses that investigated the relationship between cupping therapy and pain-related outcomes, published through April 2023. The methodological quality of the included meta-analyses was assessed using the AMSTAR-2 tool, while the quality of evidence was classified through the GRADE system. The results revealed a complex scenario regarding the quality of the available evidence.

Of the 14 meta-analyses analyzed, only one was classified as high methodological quality (7%) and one as moderate quality (7%), while five were considered critically low quality (36%) and seven of low quality (50%). In terms of evidence quality by the GRADE system, no study presented high-quality evidence. However, 8 moderate-quality evidence outcomes were identified, 6 of low quality, and 7 of very low quality, totaling 21 outcomes analyzed. The conditions that showed more robust evidence include neck pain, with two moderate-quality evidence outcomes, four of low quality, and two of very low quality.

For low back pain, two moderate-quality evidence outcomes, one of low quality, and four of very low quality were found. Knee osteoarthritis presented three moderate-quality evidence outcomes, proving to be the condition with the best scientific support for the use of cupping therapy. The evidence mapping also revealed that cupping therapy showed efficacy in the treatment of general chronic pain, with one moderate-quality evidence outcome, while for chronic low back pain and herpes zoster, only low and very low-quality evidence, respectively, was found. The proposed mechanisms to explain the effects of cupping therapy include neurological, hematological, and immunological theories.

From a neurological standpoint, it is suggested that cupping therapy induces systemic relaxation and increases the production of endogenous opioids in the brain, improving pain control. The technique may also elevate pressure pain thresholds and regulate the expression of heat shock proteins and β-endorphins. Hematologically, cupping therapy can increase blood volume and tissue oxygenation at the treated site, in addition to affecting blood flow dynamics and dermal vascular arrangement. The immunological aspect involves the regulation of local immunomodulation, where stimulation of the skin surface transforms physical signals into biological ones, activating the neuroendocrine-immune system.

The clinical implications of these findings are significant. Although no high-quality evidence was found, the moderate-quality evidence suggests that cupping therapy can be considered a valid therapeutic option for the management of certain painful conditions, particularly when integrated into multimodal treatment approaches. The safety of the technique, with low rates of reported adverse events, adds value to its clinical applicability. However, the study also identified important limitations.

The overall methodological quality of the included meta-analyses was considered low, mainly due to the absence of protocol registration, inadequate information on funding of the original studies, and insufficient explanation of risk of bias in the discussion of results. In addition, restriction to English-language literature may have resulted in the exclusion of relevant studies, and the focus only on pain-related outcomes may have overlooked other potential benefits of cupping therapy. The study concludes that, despite the limitations in evidence quality, cupping therapy represents a promising, safe, and effective therapeutic modality for the non-pharmacological management of pain. The authors emphasize the need for future higher-quality research to validate and strengthen current evidence, as well as to better elucidate the mechanisms of action of cupping therapy.