Polygala, specifically Polygala tenuifolia (commonly known as Yuan Zhi in Traditional Chinese Medicine), has a long history of use as a traditional remedy for insomnia and sleep disturbances. In TCM, Polygala is considered a "shen calming" herb, thought to nourish the heart and ease restlessness, anxiety, and disturbed sleep. Historical texts and materia medica dating back centuries reference its use for calming the mind and supporting restful sleep, often as part of multi-herb formulations.

Modern scientific evidence to support Polygala’s efficacy for insomnia is limited but growing. A handful of animal studies suggest that extracts of Polygala tenuifolia may exert sedative and anxiolytic effects, possibly by modulating neurotransmitters such as GABA and serotonin. However, high-quality human clinical trials are lacking, and most available studies are preclinical. Thus, while the traditional basis for its use is strong, the current scientific evidence is preliminary and not robust enough to confirm effectiveness.

In summary, Polygala’s use for insomnia is primarily justified by tradition, with a modest but inconclusive body of scientific research suggesting possible benefit.