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American skullcap (Scutellaria lateriflora): an ancient remedy
for today's anxiety?
Christine Brock1
Julie Whitehouse1
Ihab Tewfik1
Tony Towell2
1 School of Life Sciences
2 School of Social Sciences, Humanities and Languages
This is an electronic final author version of an article first published in British
Journal of Wellbeing, 1 (4). pp. 25-30, July 2010.
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http://www.britishjournalofwellbeing.com/cgi-bin/go.pl/library/abstract.html?uid=49168
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1
British Journal of Wellbeing • Vol 1 No 4 • July 2010
American skullcap (Scutellaria lateriflora): an ancient remedy for today’s anxiety?
Christine Brock a, *, Julie Whitehouse b, Ihab Tewfik c, Tony Towell d
a * Department of Life Sciences Research, University of Westminster, 115 New
Cavendish St, London W1W 6UW, United Kingdom. E-mail:
C.Brock@westminster.ac.uk, tel. +44 020 7915 5000, fax 02079110208
b Department of Herbal Medicine and Nutritional Therapy, School of Life Sciences,
University of Westminster, 115 New Cavendish St, London W1W 6UW, United
Kingdom. E-mail: whitehj@wmin.ac.uk
c Department of Human and Health Sciences, School of Life Sciences, University of
Westminster, 115 New Cavendish St, London W1W 6UW, United Kingdom. E-mail:
I.Tewfik@westminster.ac.uk
d Department of Psychology, University of Westminster, 309 Regent Street, London
W1B 2UW, United Kingdom. E-mail: A.Towell@westminster.ac.uk
*Author for correspondence
Abstract
Anxiety is a common but potentially serious disorder as it can lead to somatic and social
dysfunction. Orthodox anxiolytics are associated with unpleasant side-effects and
dependency. American skullcap (Scutellaria lateriflora) is a popular herb in traditional
medicine systems and the western materia medica for anxiety and related disorders.
Preliminary clinical and in vitro research provides encouraging support for its potential
as a safe, well-tolerated and effective alternative.
Key points
• Research has demonstrated the capacity of American skullcap’s flavonoids to
bind to brain receptors implicated in modulation of anxiety
• In one year up to one in six UK adults in the UK may suffer from an
unexplained psychological disorder, the most common being anxiety
• Anxiety and stress are common reasons for visits to herbal medicine
practitioners.
• An initial survey of UK and Ireland herbal medicine practitioners indicated
American skullcap as their treatment of choice for anxiety and related disorders
• Quality control of the raw herb and its commercial products is important.
Key words: Anxiety, Stress, Herbal Medicine, Flavonoids
2
Introduction
Anxiety is ‘an unpleasant emotional state ranging from mild unease to intense fear’
(B.M.A., 2002). Although anxiety is a normal response to stressful situations it can be
seen as a chronic manifestation of a modern lifestyle that includes repeated daily
stressors (Pavlovich, 1999). It is a potentially serious disorder as it can precipitate a
number of health problems and difficulties in social and occupational functioning
(Fricchione, 2004).
Physical symptoms of anxiety include pallor, sweating, hyperventilation, diarrhoea,
irritable bowel, flushing, dysphagia, palpitations, nausea and muscle tension (B.M.A.,
2002). Furthermore, Pitsavos et al. (2006) found strong evidence for a positive
association between severity of state anxiety in both men and women and increased
levels of plasma pro-inflammatory cytokines, coagulation factors, C-reactive protein
and white blood cells. Alleviation of these adverse effects on health is important.
Many orthodox anxiolytic treatments can have unwanted side-effects. Benzodiazepines,
for example, have been linked to muscle weakness, amnesia, headaches, vertigo, urinary
retention, slurred speech and gastro-intestinal disturbances. They may lead to tolerance
and physical and psychological dependence and are considered to be dangerous to use
long-term (BNF, 2008). The side effects of antipsychotics, sometimes prescribed in the
short-term for severe anxiety, include tremor, abnormal face and body movements and
restlessness (BNF, 2008). Beta-blockers may be prescribed for relief of physical
symptoms, such as tremors and palpitations, associated with anxiety. However, side-
effects are similar to those of benzodiazepines and may additionally include
bradycardia, vasoconstriction and heart failure (BNF, 2008). There is therefore a need
for safe alternatives, without unwanted side-effects.
American skullcap (Scutellaria lateriflora) (Figure 1) is one of the most commonly
used herbs by western medical herbalists, particularly for anxiety and related conditions
(Bergner, 2002-2003). This article discusses its clinical application, and reviews both
scientific and anecdotal evidence in support of its traditional use for anxiety.
American skullcap (Scutellaria lateriflora L)
Scutellaria lateriflora is a perennial herb belonging to the Lamiaceae (mint) family and
is one of 360 known skullcap species worldwide (Malikov and Yuldashev, 2002). It
grows on wetlands and is indigenous to North America and Canada where it is widely
distributed (U.S.D.A.). It also grows on riverbanks and marshes in northern Iran
(Yaghmai, 1988) and is grown commercially worldwide (Wills and Stuart, 2004).
It was an important North American ethnobotanical medicine for use in anxiety, hysteria,
phobias, panic attacks, tension, sleep disorders and stress (Felter and Lloyd, 1898; Joshee
et al., 2002). It has also been used for centuries in both Persian and Cherokee folk
medicine for nervous disorders of the digestive tract (Khosh, 2000) and Native
American women traditionally used it for premenstrual tension (Indiana Medical
History Museum, undated). The herb is also used extensively and highly valued in
traditional western herbal medicine. It was mentioned in the first American materia
medica in 1785 but had been in longstanding use as a home remedy before then (Lloyd
1911).
3
In modern western herbal medicine it is used most commonly for insomnia, nervous
disorders and digestive disturbances (Greenfield and Davis (2004). Bergner (2002-
2003) proposes its action is primarily as a trophorestorative on the central nervous
system, allowing relaxation following nervous exhaustion. It is also used for barbiturate
and tranquiliser withdrawal symptoms (Joshee et al., 2002), fibromyalgia, anorexia
nervosa, post-stroke paralysis, atherosclerosis, hyperlipidaemia, allergies, skin
conditions and inflammation (Natural Medicines Comprehensive Database., 2008).
Figure 1: Scutellaria lateriflora L.
Following reports of liver damage from use of S. lateriflora products there was a
decline in its popularity in the1970s and 1980s (McCaleb, 2004). The cause of the
hepatotoxicity was likely to be due to contamination with Germander (Teucrium)
species (De Smet, 1999) which contain pyrrolizidine alkaloids (McCaleb, 2004). S.
lateriflora is not associated with hepatotoxicity.
Since 2002 there has been a sharp increase in demand for S. lateriflora , possibly due to
it being favoured as an anxiolytic alternative to the previously popular Piper
methysticum (kava kava), which, due to toxicity fears, is no longer widely prescribed by
herbalists in Europe (Greenfield and Davis, 2004).
Scutellaria baicalensis (Georgi) (Baikal skullcap) root is extensively prescribed in
traditional Chinese and Japanese (kampo) medicines, particularly to treat inflammatory
diseases, and has been widely researched in relation to its efficacy and pharmacological
properties. Although S. lateriflora is a popular herb in western herbal medicine and
contained in many herbal formulations (Joshee et al., 2002), particularly for anxiety and
stress, relatively few scientific studies of this herb exist (Cole et al., 2008).
4
S lateriflora is the practitioner’s choice for treating anxiety
Results of a survey conducted by the authors amongst herbal medicine practitioners in
the UK and Ireland indicate that S. lateriflora is considered to be an effective
intervention for anxiety and stress and is commonly prescribed for these conditions and
related co-morbidities.
The survey aimed to gather information on the extent of, and indications for, current use
of S. lateriflora, its perceived effectiveness and safety. Herbal medicine practitioners
were selected from the membership list of the National Institute of Medical Herbalists
(NIMH). All members with identifiable email addresses were contacted (n = 377) and
responses were received from 62 (a 16% response rate).
Results indicate primary use of S. lateriflora for relief of anxiety, stress or associated
symptoms with 84% of respondents saying they would prescribe it for specific anxiety
disorders and 100% for anxiety-related co-morbidities. Twenty five respondents said it
is their preferred herb for anxiety (Figure 2). One respondent indicated their preferred
anxiolytic as being S. baicalensis. In common with many other Scutellaria species, S.
lateriflora and S. baicalensis have similar phytochemical constituents, although in
different ratios and quantities, which may explain the differing traditional uses amongst
Scutellaria species. For instance, S. baicalensis contains 800 times more scutellarin
than S. lateriflora (Cole et al., 2008). Although S. baicalensis is most commonly used
for inflammation (Joshee et al., 2002) both S. lateriflora and S. baicalensis have been
found to inhibit cyclooexgenases in vitro (Gafner et al., 2004; Jia et al., 2007). S.
lateriflora is reported to have been traditionally used for inflammation. The Iroquai
tribe, for example, used it ‘to keep the throat clear’ (Joshee et al., 2002). Conversely, S.
baicalensis root is reported to have been used as a sedative (Liao et al., 1998).
All respondents who regularly prescribe S. lateriflora (92%) identified use for anxiety
as distinct from depression and whilst some reported it useful in depression (16%) also,
several respondents reported it as unsuitable for significant depression.
Use for insomnia and sleep-related disorders was specifically reported by 57% of
respondents. Other conditions for which it was used include fear and panic states,
migraine and other headaches, muscular tension, physical and mental exhaustion and
post viral fatigue. It was also reported by 3 practitioners as useful in emotional
disturbance in menopause and in premenstrual syndrome.
The survey respondents reported the herb as being used over a range of time periods
from immediate short term use to several years, with positive response expected to be
experienced by the patient within the first two weeks and persisting throughout the
period of use.
The benefits most often reported by patients to their practitioners were feeling calmer,
improved sleep patterns and quality, and better able to cope in stressful situations. Other
positive effects were mood elevation, increased energy, being more focused and feeling
generally more relaxed.
5
Figure 2: Anxiolytic herbs as preferred by survey respondents
Key: Avena = A. sativa (oats); Crataegus = Crataegus spp. (hawthorn); Hypericum = H. perforatum (St
John’s wort); Lavandula = Lavandula spp. (lavender); Leonorus = L. cardiaca (motherwort); Matricaria =
M. recutita (German chamomile); Melissa = M. officinalis (balm); None = no preference; Passiflora = P.
incarnata (passion flower); Piper = Piper methysticum (kava-kava); S. baicalensis (baikal skullcap); S.
lateriflora (American skullcap); Stachys = S. betonica (wood betony); Tilia = Tilia spp (linden);
Valeriana = Valeriana officinalis (valerian); Verbena = Verbena officinalis (vervain).
Tinctures made from either fresh or dried organic and non-organic herb are the
preferred mode of administration by respondents. The main reason is a belief that
tinctures are more effective and they are better for patient compliance and generally
more convenient than dried herb. Many (63%) said they prefer to use organic S.
lateriflora and 42% prefer tinctures made from the fresh herb, believing this to be the
most effective.
All respondents prescribe the herb in combination with other herbs. Only 9% of the
respondents regularly prescribed S. lateriflora as a single herb so it is difficult to draw
conclusions about the perceived actions of S. lateriflora used on its own. Nevertheless
the practitioners appear to be confident in attributing specific actions and responses to S.
lateriflora as distinct from other herbs in a mixture in having the anxiolytic actions.
Furthermore, respondents prescribing it as a single herb reported positive feedback from
their patients such as reduced anxiety, fewer and less intense panic attacks, feeling of
well-being, feeling more positive, more able to cope. Interestingly, one practitioner
prescribing the herb in combination reported a relapse in symptoms of anxiety in some
patients whenever it was removed from the mix.
The herb was reported as being well tolerated with no reports of toxicity and only minor
and infrequent side effects (reported by 7 users), including daytime drowsiness, mild
digestive upset and vivid dreaming. It is uncertain whether any of these side effects
were in fact due to S. lateriflora.
It is recognised that the response rate (16%) was low and survey respondents include
only those replying to email contact and therefore may not be representative of all UK
6
and Ireland herbal practitioners. The poor response rate and the propensity of
respondents to administer S. lateriflora in combination with other herbs make it
impossible to rely on evidence regarding the efficacy of the herb from the practitioner
survey alone. A future survey could include herbal practitioners from other professional
bodies such as the Council of Practitioners of Phytotherapy. In addition contact with
herbalists internationally may provide a more useful indication of the benefits of the
herb.
Preparations and dosages used.
Preparations of S. lateriflora are made from the aerial parts and are sold in the form of
tinctures, teas and tablets; and capsules containing powders, liquids or freeze-dried
material. Dosages vary according to extraction, marc: menstrum ratio, practitioner
preference and preparations used but average at around I g equivalent dry weight per
dose three times daily (Natural Medicines Comprehensive Database., 2008).
Preparations from fresh herb are thought to be most effective (Felter and Lloyd, 1898;
Kuhn and Winston, 2001; Yarnell and Abascal, 2001).
Contraindications and side-effects
Due to its potential sedative action (Greenfield and Davis, 2004) it may be advisable to
refrain from using S. lateriflora in combination with other sedatives, including alcohol
and benzodiazepines. It is not possible to comment on the safety of its use in
pregnancy.
Anxiety: the demand for herbal treatment
In one year up to one in six adults in Great Britain may suffer from a medically
unexplained psychological disorder, the most common being anxiety (men 4%; women
5%), depression (men 2%; women 3%) or both experienced at the same time (men 7%;
women 11%). These figures indicate that anxiety and depression are more prevalent in
women than in men (Office for National Statistics, 2006). Herbal medicine is used
more frequently by women than by men (Gunther et al., 2004) and, according to a
survey in the United States (del Mundo et al., 2002) around 30% of visits to a
complementary and alternative medicine (CAM) practitioner were for anxiety and/or
stress. Of 664 respondents (74% of whom were females) only back pain was a more
common reason for CAM visits. As chiropractors were the most visited CAM
therapists, with medical herbalists a close second, it may be deduced that since the
chiropractors are more likely to treat back pain, the majority of visits to herbal medicine
practitioners were by women with anxiety and stress (del Mundo et al., 2002).
The potential efficacy of S. lateriflora in treating anxiety
Chemistry
S. lateriflora is rich in flavonoids, a group of phenolic compounds that are highly active
physiologically, and have been attributed with its anxiolytic effects. Baicalin, its
aglycone baicalein, wogonin and lateriflorin are the major flavonoids in S. lateriflora
(Nishikawa et al., 1999; Gafner et al., 2000; Gafner et al., 2004).
7
It also contains gamma - aminobutyric acid (GABA), an inhibitory neurotransmitter that
modulates anxiety, sleep, convulsions and mood (Rabow et al., 1995), and markedly
high levels of glutamine, a non-essential amino acid that plays an important role in
immune function – particularly in response to stress (Bergeron et al., 2005). Although
GABA does not readily cross the blood-brain barrier (Spinella, 2002), glutamine can
and may be biosynthesised to GABA by GABA-ergic neurons. The presence of
glutamine in the herb may therefore contribute to its anxiolytic activity by increasing
the availability of GABA in the central nervous system (Bergeron et al., 2005).
In vitro studies
Benzodiazepines are allosteric ligands for the GABAA receptor, a chloride channel that
is gated by GABA. They bind to the benzodiazepine site of the GABAA receptor, thus
increasing the affinity of the inhibitory neurotransmitter GABA for the GABA site of
the GABAA receptor, decreasing the likelihood of action potentials by excitatory
neurotransmitters (Rabow et al., 1995). A study (Liao et al., 1998), indicated oroxylin
A, baicalein and wogonin, which are flavonoids found in S. lateriflora, had weak
affinities for the benzodiazepine site of GABAA receptors in mouse cerebral cortex in
vitro. In another study Hui et al. (2000) tested the capacity of baicalin, baicalein,
scutellarein and wogonin to bind to the benzodiazepine site of the GABAA receptor in
homogenised rat brain. Affinity to the benzodiazepine site for scutellarein was
moderate and weak for baicalin. Contrary to results of the earlier study (Liao et al.,
1998) the binding affinities of wogonin and baicalein were strong. The authors
suggested the discrepancy may be due to differences in species and assay models used
(Hui et al., 2000).
The ability of the skullcap flavonoids to bind to the benzodiazepine site of the GABAA
receptor suggests an anxiolytic effect for S. lateriflora but studies on human tissue of
neuronal origin are needed to verify results.
Gafner et al. (2003) found extracts of dried S. lateriflora aerial parts and its flavonoids
baicalin, scutellarin, wogonin, lateriflorein, ikonnikoside I and dihydrobaicalin, had
high affinity for the serotonin7 (5-HT7) receptor in human 5-HT7 - transfected Chinese
hamster ovary cell lines. It was not known whether these extracts and flavonoids were
agonists or antagonists (Gafner et al., 2003) but 5-HT7 receptor antagonists and inverse
agonists are known to be useful in the treatment of premenstrual syndrome, sleep
disorders, appetite disorders, anxiety, phobias, panic, and stress-related disorders
(Bright et al., 2004); these are also conditions for which S. lateriflora is traditionally
used (Joshee et al., 2002; Greenfield and Davis, 2004).
Human clinical trials
To date only one clinical trial has been published on S. lateriflora. Wolfson and
Hoffmann (2003) assessed its short-term anxiolytic properties in a double-blind,
placebo-controlled crossover study of 19 healthy volunteers. Participants took either
two placebo capsules, one capsule containing 100 mg of organic freeze-dried S.
lateriflora, two capsules of these, or one capsule of 350 mg organic freeze-dried S.
lateriflora. Participants’ energy, cognition and anxiety were self-rated at various time
points up to 2 hours following administration. All three herb tests had notable effects
on subjective anxiety scores when compared to placebo. There was only a very mild
8
decline in cognition and energy with the herbs, with no adverse reactions or side-effects,
suggesting that S. lateriflora could be a valuable anxiolytic (Wolfson and Hoffmann,
2003).
More research needs to be conducted in order to assess long-term effects. Furthermore,
the authors acknowledge that the use of validated psychometric tests is needed to
determine the herb’s clinical anxiolytic effects.
Summary and evaluation of experimental results
The receptor binding affinities of flavonoids present in S. lateriflora, including
baicalein, baicalin, wogonin and scutellarein, to GABAA -BDZ receptor sites in vitro
(Liao et al., 1998; Hui et al., 2000) indicates a possible anxiolytic action for the herb as
does the presence of glutamine and the ability of certain S. lateriflora flavonoids to bind
to 5HT7 receptors in vitro (Gafner et al., 2003). The results of a survey amongst herbal
medicine practitioners on their use of the herb and of a clinical study lend further
support to its effectiveness as an anxiolytic.
The majority of in vitro findings are as a result of research conducted using individual
phytochemicals of S. lateriflora. Whilst orthodox medicine tends to employ isolated
phytochemicals, herbal medicine uses whole plant parts in the belief that there are
synergistic benefits of the multiple active constituents in a single herb (Spinella 2002).
It is likely that the efficacy of S. lateriflora is due to its multiple constituents acting in
synergy rather than to the summative activities of the constituent phytochemicals. There
is still a need for more research into the pharmacology of extracts from whole aerial
parts of the herb and the variability which may arise from the herb sourced from
different geographical regions.
Conclusions
The traditional therapeutic uses of S. lateriflora are supported by evidence from
research. A positive therapeutic benefit of the herb for anxiety is indicated by the
results of a survey conducted amongst herbal medicine practitioners; in vitro and
chemical studies; and a clinical trial, which supports its reputation for safety as well as
its efficacy as an anxiolytic.
As with all studies of herbal medicines important considerations, which may impact
upon findings are the variations in quality and quantity of any given herbal preparation
as well as the effects of other herbs in a mixture. Commercial herbal products have
been found to contain significant variations in phytochemical profile within a species.
Such variation may be according to geographic region, biodiversity, ecological
variations, cultivation, seasonality, harvesting, processing method, marc to menstrum
ratio and alcohol concentration, and storage time affecting stability, (Ciddi, 2006; Gao
et al., 2008). Stability of a herbal product is important with regard to efficacy and
safety and may be affected by various factors, such as pH, light, enzymatic degradation
(for example due to harvesting stress, heat or insects) and temperature (Gafner and
Bergeron 2005).
Furthermore, quality control of S. lateriflora is important to not only ensure high
standards of efficacy but also for reasons of safety. It is frequently adulterated with
9
germander species or other skullcap species, both deliberately (germander has a heavier
dry weight) and due to misidentification of the large number of skullcap species
(Gorman, 2008) . High Performance Liquid Chromatography (HPLC) methods can be
used for verifying its purity and quality. A characteristic profile of the HPLC
chromatogram or ‘fingerprint’, which is altered by adulteration, can be used for accurate
identification of the herb. The pattern’s relative percentage of flavonoids is the key
point to ascertain the quality and identity of S. lateriflora (Wills and Stuart, 2004).
While the results of the in vitro and chemical studies are interesting and provide clues to
the pharmacological action of S. lateriflora, more clinical studies are required to
provide better evidence of the therapeutic value of Scutellaria lateriflora as an effective
agent for anxiety and stress. It has the potential to be as important for the treatment of
anxiety as St John’s Wort has been found to be for depression. Ultimately it may
emerge as a useful and cost-effective agent to rival currently used anxiolytic
pharmaceuticals.
Acknowledgements
Thanks to all the herbal medicine practitioners who kindly gave up some of their
valuable time to respond to the skullcap survey.
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