Piper Methysticum (Kava) Attenuates Dorsal Anterior Cingulate Cortex GABA Levels in Generalised Anxiety Disorder

Generalised Anxiety Disorder (GAD) is a prevalent, chronic mental health disorder. The measurement of regional brain gamma-aminobutyric acid (GABA) offers insight into its role in anxiety and is a potential biomarker for treatment response. Research literature suggests Piper methysticum (Kava) is efficacious as an anxiety treatment, but no study has assessed its effects on central GABA levels.This study investigated dorsal anterior cingulate (dACC) GABA levels in 37 adult participants with GAD. GABA was measured using proton magnetic resonance spectroscopy (1H-MRS) at baseline and following eight weeks’ administration of Kava (standardised to 120 mg kavalactones twice daily) (n = 20) or placebo (n = 17). This study was part of the Kava for the Treatment of GAD (KGAD; ClinicalTrials.gov: NCT02219880), a 16-week intervention study.Compared with placebo, the Kava group had a significant reduction of dACC GABA (p = .049) at eight weeks. Baseline anxiety scores on the HAM-A were positively correlated with GABA levels,but were not significantly related to treatment.Central GABA reductions following Kava treatment may signal inhibitory effect, which, if considered efficacious, suggests GABA levels are modulated by Kava independent of reported anxiety symptoms. dACC GABA patterns suggest a functional role of higher levels in clinical anxiety, but warrants further research for symptom benefit. Findings suggest dACC GABA levels previously un-examined in GAD could be utilised as a biomarker for diagnosis and treatment response.