Patients who consumed kava tablets showed significant improvements in their symptoms, as measured by a commonly used psychological test.
By the end of the experiment, 26 percent of kava-consuming patients were in remission from their symptoms compared with 6 percent of the placebo group, according to the study, which was published this month in the Journal of Clinical Psychopharmacology.
Kava is less addictive and has a lower risk of side effects compared with conventional anxiety medications, according to the study.
In the study, some people taking kava reported headaches, but no other side effects were seen. Previous studies have suggested the plant may have negative effects on the liver, but liver tests in the study participants showed no problems.
Researchers also found that people's genetics may affect their response to kava. Genes that code for proteins that transport a brain chemical called GABA may play a role in this.
"If this finding is replicated, it may pave the way for simple genetic tests to determine which people may be likely to have a beneficial anxiety-reducing effect from taking kava," said Jerome Sarris, study author from the University of Melbourne.