Poria mushrooms (Poria cocos, also known as Fu Ling in Traditional Chinese Medicine) have a long history of use in East Asian herbal medicine. Traditionally, Poria is employed to "calm the spirit" (Shen), support sleep, and alleviate symptoms associated with nervous exhaustion, such as anxiety, restlessness, and insomnia. This traditional use stems from TCM theory, where Poria is thought to drain dampness and strengthen the spleen, thereby indirectly supporting mental and emotional well-being.

However, scientific evidence specifically supporting Poria's efficacy for nervous exhaustion is limited. Some laboratory studies have found that extracts of Poria cocos may exert mild sedative or anxiolytic effects in animal models, and a few in vitro studies suggest possible neuroprotective or anti-inflammatory actions. Nevertheless, there are no robust human clinical trials directly evaluating Poria for symptoms classified as "nervous exhaustion" (a somewhat antiquated term overlapping with modern concepts of burnout or chronic fatigue).

In summary, the use of Poria mushrooms for nervous exhaustion is primarily justified by traditional use rather than scientific validation. The available scientific evidence is preliminary and indirect, warranting a low evidence score.