Effects of chamomile (Matricaria chamomilla L.) on sleep: A systematic review and meta-analysis of clinical trials

OBJECTIVE: We aimed to investigate the effects of chamomile (Matricaria chamomilla L.) on sleep in this systematic review and meta-analysis of clinical trials. METHODS: PubMed, Scopus, Web of Science, and Cochrane Library were searched until August 2023. All clinical trials that investigated the effects of chamomile on sleep, either in healthy or diseased adults, were eligible to enter the study. The quality of studies was assessed using the Cochrane tool. Random-effects meta-analysis was used to pool weighted mean differences (WMD) and 95 % CI for the outcomes assessed by at least three studies with relatively consistent participants. RESULTS: The systematic review included ten studies (772 participants). Meta-analysis was conducted for the Pittsburgh Sleep Quality Index (PSQI) score and sleep length. A significant reduction in PSQI score (WMD: -1.88, 95 %CI: -3.46, -0.31, I2: 88.4 %, n = 5) was found. For other outcomes, meta-analysis was not conducted. Sleep onset latency or ease of getting to sleep were improved in three of the four studies. Daytime functioning measures, including fatigue severity index or postpartum fatigue scale, did not change in all three studies. Sleep efficiency did not change in two studies and deteriorated in one. The number of awakenings after sleep or staying asleep was improved in two of the three studies. No adverse events were reported in any of the studies although passive surveillance was used to assess adverse effects except in one study. Only one study surveyed the blinding success and tested the purity and/or potency of the used products. CONCLUSION: Chamomile improved sleep, especially the number of awakenings after sleep or staying asleep; however, it did not lead to an improvement in the duration of sleep, percentage of sleep efficiency, and daytime functioning measures. Future studies are suggested to assess objective measures.