Devil's Club (Oplopanax horridus) has a long history of use in traditional medicine among Indigenous peoples of the Pacific Northwest. It has been employed for a variety of ailments, including spiritual and emotional imbalances, which may encompass what is now described as mood swings. Some ethnobotanical records indicate that the root or bark was used in teas or poultices for calming, purification, or to address “nervousness” and “mental stress.” However, these uses are based on oral tradition and cultural practices rather than systematic clinical study.

There is currently no robust scientific evidence to support the use of Devil's Club for mood swings, depression, or other mood disorders. Most contemporary research focuses on its potential anti-inflammatory, anti-diabetic, and antimicrobial properties, rather than any psychoactive or mood-stabilizing effects. No clinical trials or pharmacological studies have demonstrated efficacy for mood stabilization or regulation.

In summary, Devil's Club is used for mood swings primarily due to tradition and anecdotal reports within certain cultural contexts, and there is only minimal evidence (level 1/5) to support its effectiveness for this purpose.