Ayurveda, the Indian traditional system of medicine uses herbs and their preparations to treat various neuropsychiatric disorders. Numerous herbs have been used for centuries in folk and other traditional medicine to calm the mind and positively enhance mood. Herbal medicine which plays an important role in developing countries, are once again becoming popular throughout developing and developed countries. Study by Sparreboom et al. revealed that use of herbal medicine is increasing enormously in the Western world. In spite of the large number of animal studies evaluating the potential anxiolytic effects of plant extracts, very few controlled studies have been conducted in a clinical setup. The efficacy and safety of utilizing these natural drugs to treat anxiety, has only just begun to be exactly tested in clinical trials within the last 10 to 15 years. For instance, both Kava-kava (Piper methysticum) and St. John’s wort (Hypericum perforatum) showed beneficial effectiveness in double blind, randomized placebo controlled trials to treat anxiety and depression. Also, extracts of valerian, hops, lemon balm and passion flower preparations have been employed for the prevention and treatment of psychiatric disorders such as anxiety, sleep disorders, convulsions, cognitive impairment and depression. The commonly used herbal remedies for treating anxiety disorders are described below.
Passiflora incarnata is a folk remedy for anxiety. The anxiolytic effects of passionflower are well documented in rodents. In randomized double-blind study, passion flower extract was effective in 18 generalised anxiety disorder (GAD) outpatients as compared to oxazepam. Also, impairment in the job performance was increased in oxazepam group as compared to Passiflora extract treated group. In another double-blind placebo-controlled study, preoperative oral Passiflora incarnata reduces anxiety in ambulatory surgery patients.
There is substantial evidence that kava has a positive effect on the symptoms of anxiety disorders. Animal studies have demonstrated anti-anxiety activity of kava. Several randomized double-blind clinical studies in generalized anxiety disorder patients showed beneficial effect of kava-kava in reducing anxiety. Kava-kava was used in numerous controlled clinical studies to treat anxiety disorders, but the subjects included in these studies were heterogeneous i.e., they were diagnosed with agoraphobia, specific phobia, social phobia, adjustment disorder with anxiety. In the study by Connor & Davidson, kava extract was compared with placebo in generalized anxiety disorder patients. In another 8-week randomized, double-blind multi-center clinical trial, the efficacy of Piper methysticum was compared with two anxiolytic drugs opipramol and buspirone in generalized anxiety disorder patients. Meta-analysis study by Pittler and Ernst reinforced the anxiolytic effect of kava in generalized anxiety patients and indicated a significant reduction in anxiety parameters evaluated by the Hamilton Anxiety (HAMA) scale.
St. John’s wort (Hypericum perforatum)
St. John’s wort is a popular supplement for treating depression but is much less popular for treating anxiety disorders. Studies conducted by Flausino et al. and Singewald et al. have shown that chronic administration of Hypericum perforatum induced an antidepressant-like effect in Magnesium-depleted mice in the forced swim test and anxiolytic effect in the elevated T-maze and the light/dark transition test. St. John’s wort administration resulted in anti-anxiety effect in animal models of restraint stress and sleep deprivation. Hypericum perforation inhibits the reuptake of serotonin, noradrenaline, dopamine and modulates neuronal excitability via glutamatergic and GABAergic mechanisms. Studies specifically testing the effects of St. John’s wort on patients with anxiety are extremely limited. The evidence of positive effects of St. John’s wort on anxiety disorders is weak. No placebo-controlled, randomized, double-blind trials have shown St. John’s wort to be effective in treating generalized anxiety disorder, post-traumatic stress disorder, obsessive-compulsive disorder (OCD), or phobias. Volz et al. showed that Hypericum extract to 149 out patients diagnosed with somatization disorder, undifferentiated somatoform disorder, or somatoform autonomic dysfunctions, significantly reduced anxiety scores in HAMA scale. Another open-label uncontrolled observation with 500 subjects showed beneficial effect of St. John’s wort extract in reducing anxiety disorder symptoms in patients diagnosed with depression comorbid with anxiety. However, stronger evidence is needed before St. John’s wort should be considered as a treatment option for patients with diagnosable anxiety disorders.
Valerian is one of the most popularly used herbal medicines for insomnia and is also used to treat anxiety. Hydroalcoholic and aqueous extracts of valerian roots have shown affinity for the GABA-A receptor in the brains of rats. In humans, valerian has been successful in the treatment of insomnia and tension. Andreatini et al. compared the extract of Valeriana officinalis L. (81mg of valepotriates as active ingredients) with placebo and diazepam (6.5 mg) in patients with generalized anxiety disorder (DSM-III-R, 12 patients per group). Only the diazepam and valepotriates groups showed a significant reduction in the psychic factor of HAMA scale and the preliminary data obtained in the present study suggest that the valepotriates may have a potential anxiolytic effect on the psychic symptoms of anxiety. The limitations of this study are small sample size and a low dose of diazepam, such studies should be replicated with improved methodological design.
Extract of Ginkgo biloba (EGb 761) significantly reduced the detrimental effect of learned helplessness in a subsequent conditioned avoidance task. In the elevated plus maze, senescent mice treated with EGb 761 spent more time in open arms than those treated with vehicle control compared a standardized extract of Ginkgo biloba L. (EGb 761) in doses of 480mg and 240mg with placebo for four weeks, involving patients with generalized anxiety disorder and adjustment disorder with anxious mood (DSM-III-R). The two doses of EGb 761 showed a greater reduction in HAMA scores compared to placebo, as well as a statistically significant reduction in somatic symptoms compared to baseline (which was not observed in the placebo group).
Galphimia glauca Cav. is a plant used in Mexican traditional medicine as a “nerve tranquilizer”. Previous studies have demonstrated anxiolytic effect of methanolic extract from this plant species. Herrera-Arellano et si. conducted a controlled study comparing the extract Galphimia glauca Cav. with lorazepam in patients with generalized anxiety disorder with 72 and 80 patients per group, respectively. Both groups of patients showed a significant reduction in scores of HAMA, without any difference between treatments.
Matricaria recutita (chamomile)
Chamomile is one of the most popular single ingredient of herbal teas, or tisanes. Chamomile tea, brewed from dried flower heads is used traditionally for several medicinal purposes like gastrointestinal tract ailments. Other uses include allergic rhinitis, attention deficit-hyperactivity disorder (ADHD), restlessness, insomnia, dysmenorrhea, mastitis and varicose ulcers. Chamomile contains flavonoids, which exert benzodiazepine-like activity and also has a phosphodiesterase inhibitory action, which leads to increased cAMP levels. A recent study evaluated the efficacy of a standardized extract of Matricaria recutita (L), compared with placebo for eight weeks in patients with mild to moderate generalized anxiety disorder (DSM-IV). There was a statistically significant reduction in the scores of HAMA in the group treated with extract compared to placebo-treated group.
Astragalus membranaceus (AM) is a useful Korean herb that has been clinically prescribed for stress-related illness. AM significantly restores learning and memory deficits in chronically stressed rats. In the elevated plus maze, AM treatment significantly increases the time spent in the open arms compared to control group. It also enhanced choline acetyltransferase (ChAT) expression in stressed rats. No clinical data is available for its anxiolytic effect. But one clinical study demonstrated the protective effect of astragalous on oxidative stress status in maintenance of hemodialysis patients.