Neurocognitive effects of kava (Piper methysticum) : a systematic review

Rationale Kava (Piper methysticum) elicits dose-dependent psychotropic effects and thus may potentially deleteriously affect cognitive performance. Clinical trials have assessed the effects of kava on cognition, however, to our knowledge no systematic review has been conducted in this area. Objective To systematically review the effects of kava on cognition, providing an analysis of the individual study's methodological quality, results and effect sizes. Methods A systematic review was conducted of publications up to June 15th 2010, using the electronic databases MEDLINE, PsychINFO, CINAHL, Web of Science and The Cochrane Library. The search criteria involved kava and cognition related terms, e.g. memory and attention. Results Ten human clinical trials met inclusion criteria (acute n=7, chronic n=3). One acute study found that kava significantly improved visual attention and working memory processes while another found that kava increased body sway. One chronic study found that kava significantly impaired visual attention during high-cognitive demand. Potential enhanced cognition may be attributed to the ability of kava to inhibit re-uptake of noradrenaline in the pre-frontal cortex, while increased body sway may be due to GABA pathway modulation. Conclusions The majority of evidence suggests that kava has no replicated significant negative effects on cognition.