Herbal Remedies Healthcare professionals and scientists have carefully prepared this ALtruis Biomedical Network-affiliated site, intended for informational purposes only . The bright yellow flower of the plant supposedly has its brightest appearance on June 24th, the birthday of St. John, thus giving it his name. Many of the substances in the brain that are affected by St. John's wort are neurotransmitters, substances that mediate the signal that is passed from one nerve to another.
Depression is thought to result from abnormal neurotransmitter activities.
Because several neurotransmitters have been associated with depression, a given treatment may or may not be effective in an individual. There is no way at the present time to determine which neurotransmitter is affected in a given individual. Therefore, St. John's wort will not be effective for everyone with depression. It generally takes at least four weeks for an improvement in mood to be seen. Although it has been studied for its activity against various viruses including HIV , there is no evidence that it has antiviral activity.