American skullcap (Scutellaria lateriflora L):a study of its effects on mood in healthy volunteers

American skullcap (Scutellaria lateriflora) has long been an important herb in North American traditional medicine systems and western materia medica for anxiety and related disorders. A previous clinical study assessing acute effects of S. lateriflora indicated it has anxiolytic actions with minimal loss of energy or cognition. The aim of the present study was to extend these findings by determining the putative mood enhancing effects and safety of S. lateriflora following its chronic administration to healthy volunteers. Based on a randomised, double-blind, placebo-controlled crossover design, it examined the effects of S. lateriflora on psychologic symptoms using the Beck Anxiety Inventory (BAI) and the Profile of Mood States (POMS) questionnaires, and its potential physiological effects on stress by measuring free cortisol levels in saliva, at baseline and following administration of S. lateriflora or placebo. Liver function was assessed at the same time points by measuring levels of serum alanine aminotransferase (ALT). Pre and post intervention blood pressure and pulse rate were also measured. Freeze-dried S. lateriflora for use in the present study was authenticated by the use of high performance liquid chromatography.

Participants (n = 43) were randomised to either freeze-dried S. lateriflora (350 mg) or Urtica dioica folia (300 mg) placebo three times daily for 14 days. There was a 7 day washout period prior to crossover. Analysis of results was from 31 participants completing the study. Results from the BAI demonstrated no significant difference between S. lateriflora and placebo (p = 0.191) in anxiety scores. The results from the POMS factors demonstrated there was no significant difference between S. lateriflora and placebo in scores for Tension-Anxiety (p = 0.473), Anger-Hostility (p = 0.070) or for Depression-Dejection (p = 0.067). Overall results from subjective measures of global mood as measured by Total Mood Disturbance (TMD) on the POMS also demonstrated no significant difference between S. lateriflora and placebo (p = 0.137). Additionally, the POMS showed there was no reduction in energy or cognition following chronic administration of S. lateriflora, evidenced by there being no difference between S. lateriflora and placebo for Vigour-Activity (p = 0.244) and Confusion-Bewilderment (p = 0.838) scores respectively. From inspection of the means for both BAI and the POMS factors, however, there was an enhanced effect of S. lateriflora compared to placebo in those who took the placebo first (n = 15) and an enhanced effect of placebo compared to S. lateriflora for those who took S. lateriflora first (n = 16) suggesting a residual effect of S. lateriflora due to insufficient washout. There was no significant difference between S. lateriflora and placebo (p = 0.524) in salivary cortisol measurements, suggesting no attenuation of the hypothalamic-pituitary adrenal (HPA) axis by S. lateriflora. The ALT measurements revealed no significant difference between S. lateriflora and placebo (p = 0.801), suggesting there was no acute toxicity from S. lateriflora. Furthermore, there was no significant difference between S. lateriflora and placebo in effects on systolic (p = 0.410) or diastolic (p = 0.834) blood pressures or pulse rate (p = 0.144), all of which remained within the normal range for healthy adults. According to the participants’ diary reports, there were no adverse reactions and only mild and infrequent side-effects, which may not have been attributable to S. lateriflora.

The results suggested that S. lateriflora may have anxiolytic and mood enhancing effects in some individuals without notable side-effects or reduction in energy or cognition. Contrary to anecdotal evidence, there was no worsening of depression following administration of S. lateriflora. Further research is needed in a larger study population, using a sample with self-reported and/or diagnosed anxiety and mood disturbances, in order to further determine the effects of the herb on these paradigms.