When kava is combined with alcohol, reports vary on whether this amplifies the short-term negative effects of alcohol consumption.[1][2] Mixing kava and alcohol may increase both the sedative effects and the liver damage caused by either alone.[3]
One clinical study, in which kava was combined with St. John's Wort (990 μg of hypericin and 50 mg of kavalactones per capsule, taken 3 times a day for 4 weeks), found a reduction of depression-related symptoms of anxiety. There were also some reports of heightened emotional sensitivity and disturbed sleep in individuals taking the combination, but no conclusions could be made regarding the combination’s synergistic effects.[4]