St. John's wort is a plant native to Europe with yellow, star-shaped flowers. It's most commonly used for depression and conditions that sometimes go along with depression such as anxiety, tiredness, loss of appetite and trouble sleeping. There is some strong scientific evidence that it is effective for mild to moderate depression.

St. John's wort is named after John the Baptist. The plant usually begins to flower around the 24th of June, the feast day of St. John the Baptist. It contains many chemicals that act on messengers in the brain that regulate mood.

Other uses of St. John's wort include heart palpitations, moodiness and other symptoms of menopause, mental disorders that present physical symptoms, premenstrual syndrome (PMS), attention deficit-hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), social phobia, and seasonal affective disorder (SAD).