Efficacy of Dang Gui for Primary Dysmenorrhea: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis, published in the Journal of Ethnopharmacology in 2024, examined the therapeutic efficacy of Dang Gui (Angelica sinensis, 当归) and Dang Gui-containing formulas for the treatment of primary dysmenorrhea — menstrual cramps without an identifiable underlying pathology. The authors synthesized evidence from randomized controlled trials to evaluate pain reduction, safety, and overall treatment response.

Why this review matters: Primary dysmenorrhea affects a substantial proportion of menstruating women, with estimates suggesting that 50–80% of women experience some degree of menstrual pain, and 10–20% describe it as severe enough to interfere with daily activities. Conventional treatment relies primarily on non-steroidal anti-inflammatory drugs (NSAIDs) and oral contraceptives, which are effective for many but not all women, and may be associated with side effects that limit long-term use. There is growing interest in complementary approaches, and Dang Gui is one of the most frequently used herbs in Traditional Chinese Medicine for gynecological conditions.

Scope of the review: The authors searched multiple databases including PubMed, CNKI, Wanfang, the Cochrane Library, and others for RCTs comparing Dang Gui-based interventions (alone or in formula) against placebo, no treatment, or conventional therapy for primary dysmenorrhea. From an initial pool of several hundred records, 12 RCTs involving a total of 1,024 participants met the inclusion criteria. The authors extracted pain scores, assessed study quality using the Cochrane Risk of Bias tool, and conducted a meta-analysis where the data were sufficiently homogeneous.

Pain Reduction

The pooled analysis demonstrated that Dang Gui-containing formulas were associated with a statistically significant reduction in pain intensity compared to control conditions. The effect size was modest — clinically meaningful for some women but not a dramatic or universal response. When analyzed by formula type, Dang Gui Shao Yao San (当归芍药散) showed the most consistent signal across the included studies.

Safety Profile

Adverse events reported across the included trials were generally mild and infrequent. The most commonly reported side effects were mild gastrointestinal discomfort, including nausea and loose stools. No serious adverse events were attributed to Dang Gui-containing formulas. However, the authors cautioned that the small sample sizes and short treatment durations of the included trials mean that rare adverse events could not be reliably detected.

Mechanisms of Action

The review also summarized the preclinical evidence for Dang Gui's mechanisms. The herb's active compounds — particularly ferulic acid, ligustilide, and polysaccharides — have demonstrated anti-inflammatory effects via COX-2 inhibition, antispasmodic effects on uterine smooth muscle, and vasodilatory properties that may improve uterine blood flow. These findings provide a plausible biological basis for the clinical observations and align with the TCM understanding of Dang Gui as a Blood-nourishing and pain-relieving herb.

While this review provides a useful synthesis of the available evidence, several important limitations should be considered when interpreting the findings.

Small Sample Sizes

Most of the included trials had fewer than 100 participants. Small trials are more susceptible to random error and may overestimate treatment effects. The total pooled sample of 1,024 participants, while reasonable for a meta-analysis, is not large enough to provide definitive answers.

Inadequate Blinding

Many trials were described as "single-blind" or did not report blinding procedures in sufficient detail. Unblinded or poorly blinded trials tend to show larger treatment effects for subjective outcomes such as pain, which is particularly relevant for dysmenorrhea research.

Heterogeneity of Interventions

The included studies varied considerably in formula composition, dosage form (decoction, granules, tablets), treatment duration, and dosing frequency. This heterogeneity makes it difficult to determine the optimal formulation, dose, or treatment regimen, and limits the generalizability of the pooled estimates.

Inconsistent Outcome Measures

Different trials used different pain scales (Visual Analog Scale, Numeric Rating Scale, verbal rating scales) and assessed outcomes at different time points. This variability limits the ability to pool data meaningfully and complicates the interpretation of the meta-analysis results.

Publication Bias

As with many areas of TCM research, there is a risk that small trials with negative or null results were never published, particularly in Chinese-language journals. If present, publication bias would cause the pooled estimate to appear more favorable than the true underlying effect.

Short Follow-Up Duration

Most trials assessed outcomes over only a few menstrual cycles. Whether the observed benefits persist with longer-term use, and whether long-term safety is maintained, remains unknown. This is an important gap for a condition that is typically recurrent and chronic.

Given the current state of the evidence, the clinical implications of this review are best described as cautiously suggestive rather than definitive:

• Modest evidence of benefit: Dang Gui-containing formulas may offer modest pain relief for some women with primary dysmenorrhea, but the evidence is not yet strong enough to support routine clinical recommendations.
• Formula selection matters: Dang Gui Shao Yao San has the most consistent evidence among the studied formulas. However, in TCM practice, formula selection should be based on individual pattern diagnosis rather than a one-size-fits-all approach.
• Not a substitute for standard care: Dang Gui should not be used as a replacement for conventional medical evaluation and treatment. Women with severe or persistent dysmenorrhea should undergo appropriate medical assessment to rule out secondary causes.
• Need for better research: Adequately powered, multi-center, double-blind, placebo-controlled trials with standardized Dang Gui preparations, consistent outcome measures, and longer follow-up periods are needed before firm conclusions can be drawn.
• Individualized approach: For women considering TCM for dysmenorrhea, consultation with a qualified practitioner who can assess their specific pattern presentation is strongly recommended over self-prescription.