I tried Kava and still have a tincture in my herb cabinet.
I read online about the liver thing and then twigged that might explain why whenever I took it my stools turned out yellow. Same with cashews which have a toxin in them.
I decided this was not a good thing and so I quit using it.
I found an alternative which is hop tea with marigold, damiana and bucchu, proportions 8:4:2:1 by volume of dry herb. This mix is a very mild tranquiliser (hops) and nerve tonic (damiana) with immune tonic (marigold) and urinary antiseptic and anti-infective (bucchu). I find it helps especially during a rubbish patch.
Another one is cramp bark tincture, which is a mild but effective anxiolytic especially good at alleviating cramps. Though attention to mineral balance is always recommended for cramps (especially Ca / Mg & Na / K).
Kava tincture, I discovered, is very good for gently euthenasing fish with minimal suffering. Tells you something...