Sweet flag (Acorus calamus) has a long history in traditional medicine systems such as Ayurveda and Traditional Chinese Medicine. In these traditions, it has been used for a variety of neurological and psychological conditions, including anxiety, stress, and nervousness. The plant's rhizome is considered to have calming and sedative properties, and it is sometimes prescribed as a remedy to "soothe the mind" or help with insomnia and restlessness.

The traditional use of sweet flag for anxiety is based more on empirical observation and herbal doctrine than on rigorous scientific evidence. Modern studies on sweet flag are limited, especially with respect to its anxiolytic (anti-anxiety) effects. Some preclinical studies in animal models suggest that extracts of Acorus calamus may have central nervous system depressant activity and could potentially reduce anxiety-like behavior; however, results are preliminary and mechanisms are not well understood. Furthermore, sweet flag contains β-asarone, a compound that has raised safety concerns due to potential carcinogenic and neurotoxic effects in large doses or with long-term use.

In summary, the use of sweet flag for anxiety relief is primarily justified by traditional and historical practices rather than robust clinical evidence. While there is some early experimental support, the quality and quantity of evidence are low, and there are potential safety issues to consider.