Improving road safety and health: Understanding kava’s impact on driver fitness

Kava (Piper methysticum) is a traditional and culturally significant Pacific Island beverage that produces soporific relaxant effects. Kava use is increasing in the Pacific islands, and among Pacific diasporic and non-Pacific people. Users often consume the kava drink at much higher volumes than pharmacologically recommended doses (as much as 30 times greater is not unusual), with some users then driving home from kava use venues. While there has been a great deal of research using tablets (or capsules) containing selected extracted kavalactones, very little is understood about the psychopharmacological effects of kava when consumed in its natural traditionally influenced form over many hours as is typical in the Pacific community. Prompted by concerns over potential driver impairment as a result of kava use, this research involved testing the brain function of kava users over the course of a typical kava session (in terms of its duration and kava consumption volumes). The aim was to understand the effects that drinking kava had on driving safety. Participants in the active group (n=20) attended a 6-hour kava session, each drinking 3.6 litres (6.33 pints) of kava. A non-kava consuming control group (n=19) was also included in the study. At baseline, all participants were assessed with the Brain Gauge, a somatosensory tool that measures strategic, tactical and operational aspects of brain function. Re-testing was conducted after 3 hours of kava consumption, and again at the conclusion of the test period following the sixth hour of kava drinking. Analysis of the results compared changes in brain function, both between individuals and the two groups (active and control), before and after the kava drinking session. Statistical modeling was based on t-tests, Wilcoxon signed-rank test [W] and the Mann-Whitney U test (rank sum) [MW], and Bayesian analysis [BF]. The results showed that, for the active participants, the kava consumed had no statistically significant negative impact on their Focus, Accuracy, Timing Perception, Plasticity or Fatigue, when compared with the control group. When active participants (kava drinkers) were compared with other kava users’ in their group, a slight positive increase in the kava users Focus and Fatigue was noted, which could infer increased driver alertness and improved driver safety. However, the negative impact of the kava on the active participants’ Temporal Order Judgement (“how well [the] brain is able to keep track of the order of events” which is linked to a participant’s executive function) was (strongly) significant at the sixth hour: [MW=0.0119; t=0.007301; BF=6.193058]. This finding – as to the effect of kava on a person’s Temporal Order Judgement (and hence executive function) – is new, and suggests kava at traditionally consumed volumes compromises driver safety, although the nature of this impairment is vastly different to alcohol, cannabis, and other euphoric and hallucinogenic substances. Because executive function is also linked to Focus, Accuracy, Timing Perception, Plasticity and Fatigue, the finding was discussed with several psychopharmacologists, who were unable to provide an explanation for the anomaly, but noted that understanding of the effect of traditionally influenced kava consumption on cognition is still in its infancy. This study makes a new and significant contribution to understanding kava’s impacts, when consumed at traditional use volumes, on cognition, while also highlighting the huge knowledge gap that exists concerning kava psychopharmacology. The study has highlighted the need for more research to build understanding in this area, which would also assist road policing, particularly from an evidentiary perspective. The study also responded to national and international calls for research to fill the current gaps in understanding. Additionally, the study investigated the use of a Pacific language-friendly brochure-based driver awareness campaign aimed at curbing potentially unsafe post-kava drink-driving. Although well received, the brochure appeared to have minimal immediate impact on participants’ behavior. However, its value in prompting talanoa (discussion) on the subject was noted, as was the longterm nature of driver safety awareness campaigns. The study was funded by the Health Research Council of New Zealand (19/002) and the University of Waikato. Cortical Metrics, the developers of the Brain Gauge, generously assisted the project through a substantial donation of hardware and software