The Effectiveness of Kava and Saint John’s Wort for the Treatment of Anxiety and Depression

Dr. Sarris and Dr. Kavanagh conducted a systematic review of published research on the use of kava and Saint John’s Wort, which was published in The Journal of Alternative and Complementary Medicine in 2009. The study investigated the efficacy, pharmacology, and safety of kava and Saint John’s Wort as treatments for mood and anxiety disorders.


Kava (Piper methysticum) is a small leafy shrub that grows in warm, moist climates. “Kava” can also refer to the brew made from the roots of the kava plant.

The plant has traditionally been cultivated for medicinal purposes in the South Pacific because of its sedative effects. Recently, it has become available as an alternative medical treatment for anxiety in the form of kava root extracts, although the leaves are sometimes also used.

After reviewing the evidence from a number of published studies of kava, the authors of this study concluded that kava was an effective treatment for generalized anxiety disorder, but failed to find any studies that supported its effectiveness in alleviating the symptoms of obsessive-compulsive disorder, post-traumatic stress disorder, or specific phobias. Nor did the authors find any published study that supported the use of kava for depressive disorders.

Compared to other pharmaceutical substances, there is relatively little information about the pharmacokinetic effects of kava. The current evidence suggests that kava produces its anti-anxiety effects by interacting with GABA receptors in the hippocampus and amygdala, areas of the brain associated with emotion.

Kava has been banned in Canada, the United Kingdom, and the European Union because of fears that it causes liver damage. As the authors explain, “At least 93 cases of hepatotoxicity [liver damage]have been documented wherein kava may be implicated. Most cases were poorly reported and many involved the concurrent ingestion of pharmaceuticals and alcohol, excessive daily dosage or long-term administration.” Furthermore, the authors suggest that kava should be removed from over-the-counter use so that kava extracts can be standardized and monitored by health professionals.

Because of these concerns, kava should not be used alongside alcohol or by those with liver diseases.

Saint John’s Wort

Saint John’s Wort (Hypericum perforatum) is a small plant that has been used by both the ancient Greeks and Native Americans for a variety of medical purposes. Currently, extracts of Saint John’s Wort are used as an alternative treatment for depression.

According to Dr. Sarris and Dr. Kavanagh, Saint John’s Wort is “used extensively in Europe as an anti-depressant agent. In Germany [Saint John’s Wort] is one of the most prescribed antidepressant agents, with more than 100 million daily doses.”

The effectiveness of Saint John’s Wort is hotly debated. In their review, Dr. Sarris and Dr. Kavanagh found that in some cases Saint John’s Wort was more effective than synthetic antidepressants, but others believe that this is not the case. One study, the “Hypericum Depression Trial Study Group” published in 2002, found that the use of Saint John’s Wort was not more effective than placebo, but as Dr. Sarris and Dr. Kavanagh note, “What is commonly omitted in discussion of this trial is that it also found that sertaline [brand name Zoloft and Lustral]also had effects comparable to those of placebo.”

Dr. Sarris and Dr. Kavanagh concluded that Saint John’s Wort is an effective treatment of depression, but found little support that it is an effective treatment for other depressive disorders, such as Seasonal Affective Disorder (SAD) or Dysthymic disorder.

Like kava, little is known about the pharmacological effects of Saint John’s Wort. There are a variety of psychoactive substances in Saint John’s Wort (hyperforin, hypericin, etc) that appear to influence the re-uptake of the neurotransmitters serotonin, dopamine and norepinephrine similar to the way synthetic antidepressants such as Paxil and Zoloft work.

Due to the similarity between the effects of Saint John’s Wort and other antidepressants, the combination of Saint John’s Wort with antidepressants can cause dangerous side-effects, such as serotonin syndrome.


Sarris, J. & Kavanagh, D.J. (2009). Kava and saint john’s wort: Current evidence for use in mood and anxiety disorders. The Journal of Alternative and Complementary Medicine, Vol 15, No 8: 827-836.