The effect of lavender on stress in individuals: A systematic review and meta-analysis

Background: Lavender is considered as one of the medicinal plants to manage stress. Although many preliminary studies evaluated the effect of lavender on individuals??? stress level, to the best of our knowledge, we did not find a study that summarizes the results. Therefore, the present study aimed to estimate the Pooled effect of lavender on the stress level of individuals using systematic review and meta-analysis. Method: A systematic literature review based on PRISMA 2020 was performed on the SID, MagIran, Embase, PubMed, Scopus, Web of Science (WoS) databases, and Google Scholar motor engine using related MeSH/Emtree and ???Free Text words,??? including ???Lavender*???, ???Lavandula*???, ???Stress*???, ???Stress Disorders, Traumatic???, and ???Stress, Psychological??? with no time limitation until August 2021: We also searched two Iranain free local resourses including MagIran https://www.magiran.com and Scientific Information Database (SID) https://www. sid.ir. The quality assessment of studies was performed using JBI checklist. Heterogeneity among studies was quantified using I2 index and Random Effects model was used to combine the data and perform the metaanalysis. Results: In the initial search, 1520 articles were found. After excluding the irrelevant studies, finally, 21 articles with a sample size of 791 in the intervention group and 804 in the control group were included in the metaanalysis. As a result of combining the studies, stress score after using lavender in the intervention group showed a significant decrease of 0.63 ?? 0.13 (95% CI) more than that in the control group (P < 0.001). The results of subgroup analysis demonstrated that the highest standardized mean difference (SMD) before and after the intervention in the intervention group compared to the control group was related to L. angustifolia species with 0.73 ?? 0.22, student groups with 2.27 ?? 1.34, and diagnostic tool of Perceived Stress Scale (PSS) with 0.82 ?? 0.42, indicating that the difference between the groups was statistically significant (P < 0.001). Conclusion: The pooled estimation of this systematic reiew and meta-analysis revealed that lavender significantly reduces individuals??? stress. Therefore, it seems that the use of lavender can be considered as a part of a stress management programs, especially in student groups.