Sleep problems are widely prevalent and associated with various comorbidities including anxiety. Valerian (Valeriana officinalis L.) is a popular herbal medicine used as a sleep aid, however the outcomes of previous clinical studies are inconsistent. This study was conducted to update and re-evaluate the available data in order to understand the reason behind the inconsistent outcomes and to provide a broader view of the use of valerian for associated disorders. PubMed, ScienceDirect, and Cochrane Library were searched to retrieve publications relevant to the effectiveness of valerian as a treatment of sleep problems and associated disorders. A total of 60 studies (n=6,894) were included in this review, and meta-analyses were performed to evaluate the effectiveness to improve subjective sleep quality (10 studies, n=1,065) and to reduce anxiety (8 studies, n=535). Results suggested that inconsistent outcomes were possibly due to the variable quality of herbal extracts and that more reliable effects could be expected from the whole root/rhizome. In addition, therapeutic benefits could be optimized when it was combined with appropriate herbal partners. There were no severe adverse events associated with valerian intake in subjects aged between 7 and 80 years. In conclusion, valerian could be a safe and effective herb to promote sleep and prevent associated disorders. However, due to the presence of multiple active constituents and relatively unstable nature of some of the active constituents, it may be necessary to revise the quality control processes, including standardization methods and shelf life.
Keywords: anxiety; herbal medicine; insomnia; sleep; systematic review; valeriana officinalis.