Short communicationIs lavender an anxiolytic drug? A systematic review of randomised clinical trials
Introduction
Lavender (Lavandula angustifolia) has a long history of medicinal use and is purported to possess anxiolytic, sedative and calming properties (Cavanagh and Wilkinson 2002). Most commonly it is recommended for oral administration. More recently, lavender is also being employed in aromatherapy (Setzer 2009) although specific pharmacological effects of lavender aromatherapy are difficult to distinguish from any innate or learned preferences to this, or any other, odour (Bradley et al. 2009).
The chemical composition of lavender is complex and several of its constituents (e.g. linalool and linalyl acetate) have been proposed as being responsible for the perceived anxiolytic effects (Setzer 2009). In animal models, linalool has been found to inhibit GABA(A) binding reception in the CNS inducing a relaxed state (Brum et al., 2001, Hossain et al., 2004). Until recently, this activity had not been noted in human studies.
Anxiety is a common disorder (14% of the EU population suffer from one or more anxiety disorders each year (Wittchen et al. 2011)) but can be severe and debilitating, often requiring medication. Lavender may provide a gentler treatment option than conventional anxiolytic drugs. Apart from rare allergic reactions (Coulson and Khan 1999) and gastrointestinal complaints (after excessive intake) (Leung and Foster 1996), lavender intake seems to be reasonably safe.
This systematic review is aimed at critically evaluating the data from randomised clinical trials (RCTs) of all types of lavender preparations (oral, olfactory, topical) for the treatment of anxiety.
Section snippets
Methods
The following electronic databases were searched from their inception up to December 2010: Medline, EMBASE and PsychInfo (via OVID), AMED and CINAHL (via EBSCO), The Cochrane Library, and ISI Web of Knowledge. The search terms used included lavender, and anxiety or stress, and derivatives of these terms (see Appendix A for electronic search strategy). Our own departmental files and the reference lists of all selected articles were searched for further relevant studies.
Articles were included if
Results
The literature search identified 440 potentially relevant titles and abstracts. Fifteen RCTs involving 1565 participants met the inclusion criteria (Fig. 1). Where possible, between-group analyses of the main anxiety outcomes are presented in Table 1. The included studies were published between 1995 and 2010, originated from six countries and were all written in English. Sample sizes ranged from 16 to 340. The majority of trials used Lavandula angustifolia unless otherwise stated.
Eight trials (
Discussion
Our review included 15 RCTs of lavender for anxiety or stress. The majority of trials used either the STAI or HAD as the main self-reported outcome measure, whilst blood pressure, heart rate and galvanic skin response were reported as physiological outcome measures. Seven trials (Braden et al., 2009, Bradley et al., 2009, Dunn et al., 1995, Kasper et al., 2010, Kritsidima et al., 2010, Kutlu et al., 2008, Motomura et al., 2001) showed results appearing to favour the lavender intervention for at
Conclusions
Only few RCTs of lavender, for anxiety/stress are available using diverse administration methods (i.e. oral, olfactory and as a massage oil). The evidence for oral lavender is promising but, until independent replications emerge with long-term follow-up data, remains inconclusive. The use of more widely used forms of lavender administration (aromatherapy, inhalation, massage etc.) is not currently supported by good evidence of efficacy. Future trials, well-reported and adopting stringent
Conflict of interest
None.
Funding
None.
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