Clinical review
A systematic review of valerian as a sleep aid: Safe but not effective

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Summary

Valerian is an herb that is widely available in a variety of commercial preparations and is commonly used as a sleep aid. A recent systematic review and meta-analysis of valerian concluded that evidence in support of the effectiveness of the herb was inconclusive. Therefore, in an effort to more closely examine this issue, a systematic review was conducted to examine the evidence on the efficacy of valerian as a sleep aid with specific attention to the type of preparations tested and the characteristics of the subjects studied. A comprehensive search of studies investigating valerian was conducted through computerized databases and hand searches of reference lists. Standardized forms were used to summarize findings and standardized criteria were used to assess study quality. Out of 592 articles initially identified, a total of 36 articles describing 37 separate studies met criteria for review: 29 controlled trials evaluated for both efficacy and safety, and eight open-label trials evaluated for safety only. Most studies found no significant differences between valerian and placebo either in healthy individuals or in persons with general sleep disturbance or insomnia. None of the most recent studies, which were also the most methodologically rigorous, found significant effects of valerian on sleep. Overall, the evidence, while supporting that valerian is a safe herb associated with only rare adverse events, does not support the clinical efficacy of valerian as a sleep aid for insomnia.

Introduction

Approximately one-third of the adults in the United States report symptoms of insomnia; including difficulty falling and/or remaining asleep at night.1 Herbal therapies are commonly used for chronic symptoms of disturbed sleep. According to a recent survey, approximately 1.6 million Americans use complementary and alternative medical (CAM) therapies to treat their sleep disturbance.2 Valerian is among the top-selling herbals in the US and is marketed as a promoter of restful sleep. In 2005, valerian was the 13th top-selling herb in US with estimated sales totaling $3.4 million.3

A previous systematic review4 and a recent meta-analysis5 both concluded that effects of valerian on sleep were promising, but inconclusive. Previous reviews have discussed various types of valerian products without specific attention to important differences in source species and in preparation techniques used (e.g., ethanol and water versus extractions with water alone). Because the chemical constituents in valerian products vary depending on species and extraction methods,6, 7 failure to evaluate the evidence based on the type of product used may have obscured an accurate assessment of valerian effects on sleep. The species used most commonly is Valeriana officinalis, although V. edulis (Mexican valerian) and V. wallichii (Indian valerian) are also used therapeutically. In general, extractions are prepared by soaking the dried root and rhizome (the underground portion of the stem) of valerian in a solution (called a menstruum), then centrifuging or drying the mixture to extract and concentrate plant constituents. The solutions used are typically: water alone, ethanol and water, or methanol and water. The ratio of alcohol to water affects the proportion of constituents obtained. According to the American Herbal Pharmacopeia, extraction of valerenic acids requires at least 30% alcohol, whereas extraction of valepotriates requires 70% alcohol.7 The influence of extraction on the physiological effects of valerian remains unknown because the relative contributions of constituents responsible for to the plant's sedative effects have not been determined, and effects may depend on synergy of various compounds (e.g., valerenic acids, amino acids, valepotriates).8

In this review, we evaluate the research evidence on valerian as a sleep aid taking into account the types of products used. In addition, we considered whether the subjects in these studies were healthy, complained of general sleep disturbance, or met diagnostic criteria for insomnia: Diagnostic and Statistical Manual of Mental Disorders (DSM-III/IV); International Classification of Diseases (ICD-9/10); or International Classification of Sleep Disorders (ICSD). Finally, we make a recommendation about its usefulness as a sleep aid and clarify areas in which further research on valerian effects on sleep might be useful.

Section snippets

Materials and methods

The search strategy sought to obtain all relevant published data-based articles based on the following general criteria: (1) valerian root was administered orally, either alone or in combination with hops, lemon balm, or passion flower (herbs commonly combined with valerian in commercial preparations); and (2) a subjective or objective sleep measure (e.g., polysomnography or actigraphy) was at least one of the study's primary outcomes. A systematic computerized search of research databases was

Study characteristics and valerian products used

The computerized search yielded 592 article titles that were reviewed for relevance (see Fig. 1); 527 articles were excluded based on a review of the abstracts and 29 were excluded based on a review of the full text. These 556 articles were excluded for the following reasons: the articles (a) were not clinical studies (418 articles); (b) did not assess sleep as a primary outcome (65); (c) tested multiple herbs (other than hops, lemon balm, or passion flower) (6); (d) did not test an oral

Side effects and safety

No serious adverse effects occurred in these reported clinical trials of valerian (see Table 2, Table 3). The number of side effects with ethanolic valerian extracts did not differ significantly from placebo,31, 34 and tended to be fewer than benzodiazepines.13, 32 Specific side effects reported with ethanolic valerian extracts included headache, gastrointestinal (GI) complaints, morning “hangover,” diarrhea, drowsiness, exaggerated feeling of well-being, mental dullness, difficulty sleeping,

Discussion

Evaluation of the effectiveness of valerian as a sleep aid is difficult given the considerable variation among the studies in duration, design, and herbal preparation. Originally, we had intended to perform a meta-analysis of the literature available on valerian, but concluded that such an analysis was not appropriate given the variability in the research quality. In particular, evidence on valerian from both parallel-group and crossover trials should not be combined in the same meta-analysis

Conclusion

Although valerian is commonly used in the United States and Europe as a sleep aid, current evidence on the efficacy of valerian for improving sleep outcomes does not support such use. However, valerian is an apparently safe herb, with few reported side effects. Despite the lack of evidence for efficacy, these products are unlikely to cause harm other than perhaps delaying individuals from seeking the effective treatment for insomnia symptoms.

Although current evidence fails to support efficacy

Acknowledgments

The systematic review and manuscript were supported by the National Institutes of Health, grant numbers R21-AT-002108, P30-NR04001, and T32-NR07039. The authors thank Robin DiPasquale, N.D., R.H.(AHG) for consulting on this article and Cristina Fuller, Ph.D.(c), for assistance with Portuguese translation.

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