Lion's mane mushroom (Hericium erinaceus) has gained popularity as a natural supplement for cognitive and mood support, including mood swings. The primary justification for its use in this context is scientific, although the current evidence base is limited and mostly preclinical or from small-scale human studies.

Several animal studies have shown that lion's mane extract can exert antidepressant and anxiolytic effects, possibly by promoting neurogenesis and reducing inflammation in the brain. Compounds such as hericenones and erinacines are believed to stimulate nerve growth factor (NGF) synthesis, which may contribute to improved neuronal health and, theoretically, mood regulation.

A few small human trials also suggest potential benefits. For example, a 2010 study in postmenopausal women found that lion's mane supplementation reduced symptoms of anxiety and depression compared to placebo. However, these studies are limited by small sample sizes, short duration, and lack of replication. There is a notable absence of large, high-quality randomized controlled trials specifically investigating lion's mane for mood swings.

In summary, while there is some preliminary scientific evidence suggesting lion's mane may support mood regulation, the quality and quantity of evidence are low (rated 2 out of 5). More rigorous clinical research is needed to confirm its efficacy and safety for mood swings.