Original articleValerian for insomnia: a systematic review of randomized clinical trials
Introduction
Insomnia is defined as a condition of unsatisfactory quality and inadequate quantity of sleep and is characterized by difficulty initiating or maintaining sleep and early final wakening [1]. This can have adverse effects on daily functioning due to fatigue, poor concentration and memory problems [2]. Effective pharmacologic treatments include short and long-acting benzodiazepines, although many of these are associated with adverse effects, daytime sedation (hangover) and dependence with continued use [3]. Fatal overdoses are possible if taken in combination with other drugs but are rare [4]. More modern drugs such as zolpidem, zopiclone and zaleplon avoid some of the adverse effects of benzodiazepines by selective binding to receptor sites [5].
Valerian (Valeriana officinalis) is a herb that has long been advocated for promoting sleep [6]. In most countries it is marketed as an over-the-counter product for this purpose, with considerable success. Sales of valerian preparations in the US totalled $8 million between July 1997 and 1998 [7]. However, until fairly recently, clinical evidence of its value in improving sleep was almost entirely based on observational studies and anecdotal reports. A number of controlled clinical trials have been conducted during the past two decades investigating the effects of valerian on human sleep. This review aimed to summarize the evidence from all randomized, placebo-controlled, double-blind trials.
Section snippets
Materials and methods
Computerized literature searches were performed on the following databases: Medline, Embase, Biosis, The Cochrane Library, Current Contents (all from their inception to May 1999) using the search terms valerian, Valeriana officinalis, insomnia*, sleep* to identify all published articles on the subject. The reference lists of these papers were scanned for further relevant publications. Furthermore, manufacturers of valerian products and other experts working in the field were contacted and asked
Results
The search located 19 trials on valerian. Ten were excluded: four used combined preparations [9], [10], [11], [12], three were not randomized [13], [14], [15], and three did not measure sleep-related parameters [16], [17], [18]. Nine trials (reported in eight papers), therefore, met our criteria for inclusion in the systematic review. These trials are summarized in Table 1, Table 3 and described below. The first three studies examined the cumulative effects of valerian administered over
Discussion
Evaluating the efficacy of valerian for improving sleep based on randomized, placebo-controlled trials is a difficult task because of the conflicting findings and inconsistencies between studies. Nine randomized, double-blind, placebo-controlled trials meeting the inclusion criteria were found by the search. Although efforts were made to locate all available studies, it is possible that some trials were not unearthed. Since there is a tendency for negative trials to remain unpublished [27],
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