Kava for the Treatment of Generalised Anxiety Disorder: A Double-Blind Randomised Placebo-Controlled Trial

To be considered for inclusion in this study, participants will be required to meet the following criteria: * Aged between 18-70 years * Meets the Diagnostic and Statistical Manual (DSM) IV and DSM-V diagnostic criteria for generalised anxiety disorder (GAD) based on structured interview (Mini International Neuropsychiatric Interview-Plus 6 \[MINI-Plus 6\]. Note that while the MINI-Plus 6 uses the DSM-IV criteria, the same criteria are used in the DSM-V). * Presents with anxiety (Hamilton Anxiety Rating Scale ≥ 18) at the time of study entry * Fluent in written and spoken English * Provides a signed copy of the consent form Participants are ineligible to enter the trial if they have any of the following conditions: * Primary diagnosis other than GAD * Presentation of moderate to severe depressive symptoms (Montgomery-Asberg Rating Scale: MADRS ≥ 18 at time of study entry or ≥ 24 at any time during study) * Presentation of suicidal ideation (≥ 3 on MADRS suicidal thoughts domain at time of study entry or at any time during study) * Current diagnosis of bipolar disorder or schizophrenia on structured interview (MINI Plus) * Current substance/alcohol use disorder on structured interview (MINI Plus) Page 21 of 39 Commercial-in-Confidence * Currently taking an antidepressant, mood stabiliser, antipsychotic, anticonvulsant, warfarin or thyroxin, or current regular use (more than 2 days per week) of a benzodiazepine or opioid-based analgesic * Current use of a psychotropic nutraceutical (e.g. St John's wort) * Previous intolerance to kava * Three or more failed trials of pharmacotherapy for the current GAD episode * Recently commenced psychotherapy (within four weeks of study entry) * Known or suspected clinically unstable systemic medical disorder * Diagnosed hepato-biliary disease/inflammation * Elevated liver enzymes at baseline blood test * Pregnancy or breastfeeding, or trying to conceive * Not using medically approved contraception (including abstinence) if female and of childbearing age * Unable to participate in all scheduled visits, treatment plan, or other trial procedures according to the protocol (except for the optional genetic component)