Evaluating the Therapeutic Effects of Thymus vulgaris on Primary Dysmenorrhea Adolescent and Young Girls (Qualitative Evidence Synthesis)

Introduction: Primary dysmenorrhea is a common gynecological condition among Adolescent and Young girls, characterized by painful uterine cramps in the absence of identifiable pelvic pathology. This condition is associated with reduced quality of life, impaired academic performance, and limitations in daily activities. Concerns regarding the long-term use and adverse effects of nonsteroidal anti-inflammatory drugs (NSAIDs) have increased interest in complementary and herbal interventions. Purpose: This systematic review aimed to synthesize clinical and mechanistic evidence on the efficacy and safety of Thymus vulgaris for primary dysmenorrhea management through synthesis of quantitative outcomes (QES). Methods: This systematic review was conducted following PRISMA 2020 guidelines. Given the heterogeneity of interventions and outcome measures across included randomized controlled trials, statistical meta-analysis was not feasible; therefore, a narrative synthesis approach was employed to integrate quantitative findings. Confidence in evidence was assessed using the GRADE-CERQual framework for intervention reviews. A comprehensive literature search was performed in PubMed/Medline, Scopus, Web of Science, Embase, the Cochrane Library, and Google Scholar from inception to December 2025. Clinical, observational, and experimental studies examining thyme or its bioactive constituents in relation to primary dysmenorrhea were included. Methodological quality was assessed using the Critical Appraisal Skills Programme (CASP) checklist. Data were analyzed using thematic synthesis, and confidence in the review findings was evaluated using the GRADE framework. Results: A synthesis of 6 studies found that participants consistently described thyme as a familiar cultural intervention that provided tangible menstrual pain relief, with empirical reports describing reductions in pain intensity and duration comparable to conventional NSAIDs. These narratives were consistent with mechanistic evidence suggesting dual pathways carvacrol-mediated suppression of prostaglandin cascades and attenuation of the oxidative microenvironment involved in pain sensitivity. This synthesis interpreted quantitative results through a qualitative lens to elucidate perceived acceptability and underlying factors. All clinical evidence was obtained exclusively from women of reproductive age in Iranian settings (mean age 21– 24 years), and no trials recruited WHO-defined adolescents (10– 19 years). Short-term safety profiles appeared favorable over the trial duration (≤ 3 menstrual cycles), although long-term effects on pubertal endocrine maturation remain unknown. Geographic homogeneity and cultural familiarity with thyme in Iranian contexts further limits generalizability to Adolescent and Young girls around the world. Conclusion: This qualitative evidence synthesis suggests that Thymus may represent a safe and acceptable complementary option for managing primary dysmenorrhea in young girls. Further high-quality qualitative and mixed-methods research is warranted to strengthen confidence in these findings. Plain Language Summary: Why this study was conducted: Many Young girls experience painful menstrual cramps, and commonly used painkillers may cause side effects with long-term use. Therefore, safer natural alternatives are being explored. What the researchers did and found: This study reviewed existing clinical and experimental research on thyme as a treatment for menstrual pain. The findings showed that thyme essential oil, particularly at a 2% concentration, reduced pain levels similarly to ibuprofen and more effectively than placebo. Key findings: Thyme may relieve menstrual pain by reducing inflammation, lowering prostaglandin production, and decreasing oxidative stress, with no serious safety concerns reported. Further high-quality studies are needed to confirm these benefits. Keywords: thyme, dysmenorrhea, adolescent, young girls, pathophysiology, Thymus vulgaris