Plant-Based Medicines for Anxiety Disorders, Part 2: A Review of Clinical Studies with Supporting Preclinical Evidence

Research in the area of herbal psychopharmacologyhas revealed a variety of promising medicines thatmay provide benefit in the treatment of general anxiety andspecific anxiety disorders. However, a comprehensivereview of plant-based anxiolytics has been absent to date.Thus, our aim was to provide a comprehensive narrativereview of plant-based medicines that have clinical and/orpreclinical evidence of anxiolytic activity. We present thearticle in two parts. In part one, we reviewed herbal medicinesfor which only preclinical investigations for anxiolyticactivity have been performed. In this current article(part two), we review herbal medicines for which therehave been both preclinical and clinical investigations ofanxiolytic activity. A search of MEDLINE (PubMed),CINAHL, Scopus and the Cochrane Library databases wasconducted (up to 28 October 2012) for English languagepapers using the search terms ‘anxiety’ OR ‘anxiety disorder’OR ‘generalized anxiety disorder’ OR ‘social phobia’OR ‘post-traumatic stress disorder’ OR ‘panicdisorder’ OR ‘agoraphobia’ OR ‘obsessive compulsivedisorder’ in combination with the search terms ‘Herb*’ OR‘Medicinal Plants’ OR ‘Botanical Medicine’ OR ‘Chineseherb*’, in addition to individual herbal medicines. Thissearch of the literature revealed 1,525 papers, of which 53plants were included in the review (having at least onestudy using the whole plant extract). Of these plants, 21had human clinical trial evidence (reviewed here in parttwo), with the other 32 having solely preclinical evidence(reviewed in part one). Support for efficacy was found forchronic use (i.e. greater than one day) of the followingherbs in treating a range of anxiety disorders in humanclinical trials: Piper methysticum, Matricaria recutita,Ginkgo biloba, Scutellaria lateriflora, Silybum marianum,Passiflora incarnata, Withaniasomniferum, Galphimiaglauca, Centella asiatica, Rhodiola rosea, Echinacea spp.,Melissa officinalis and Echium amoenum. For several ofthe plants studied, conclusions need to be tempered due tomethodological issues such as small sample sizes, briefintervention durations and non-replication. Current evidencedoes not support Hypericum perforatum or Valerianaspp. for any anxiety disorder. Acute anxiolytic activitywas found for Centella asiatica, Salvia spp., Melissa officinalis,Passiflora incarnata and Citrus aurantium. Bacopamonnieri has shown anxiolytic effects in people withcognitive decline. The therapeutic application of psychotropicplant-based treatments for anxiety disorders is alsodiscussed, specifically Psychotria viridis and Banisteriopsiscaarti (ayahuasca), Psilocybe spp. and cannabidiolenriched(low tetrahydrocannabinol (D9-THC)) Cannabisspp.