St. John’s Wort: medicine & myth

Profiles in Norwegian science

St. John's Wort

Photo: Colourbox
St. John’s Wort flowers around Midsummer and has been used for centuries for healing various ailments.

Ilan Kelman
Agder, Norway

Since around the fourth century, many Christians have celebrated the birth of John the Baptist on June 24. More pagan, the plant St. John’s Wort tends to flower in Europe around this date, which is how it received its name.

St. John’s Wort grows around the world on land, especially in temperate regions and absent mainly from very arid areas, very cold areas, and tropical lowlands. The genus Hypericum in the family Hypericaceae refers to this plant across many species, with nicknames ranging from amber touch-and-heal to goatweed. In places, some species of this generally yellow, five-petaled flower are seen as invasive and as weeds. The Animal Health Division of the Government of Newfoundland and Labrador in Canada published a brochure titled “St. John’s Wort Poisoning in Livestock.”

Yet many people live by the adage that “a weed is just a socially challenged plant.” They swear to the medicinal powers of St. John’s Wort, with it having been used across millennia and across continents.

Claims of its healing extend to cuts, abrasions, bruises, menopause, infectious diseases, burns from the sun or fire, coughing, fatigue, anxiety, depression, mood disorders, cancer, muscle soreness, insomnia, inflammation, and nosebleeds. Millions of people use its products every year, creating an industry worth billions of dollars annually. Depending on the country, the products might be prescription, off-the-shelf supplements, or banned.

One 2017 study led by the University of Oslo’s Natural History Museum struggled to find evidence that St. John’s Wort was present in the supplements claiming to have it!

And would it really address the health concern? Cancer has numerous types and numerous causes. Anxiety might lead to insomnia or vice versa. A nosebleed differs if from a punch, air pollution, allergies, or picking one’s nose. Self-treating only a symptom with an unverified substance can do more harm than good.

One study in 2010 even looked at using St. John’s Wort for dealing with irritable bowel syndrome. The placebo performed better than the plant.

Most studied and most accepted, with the physiological reasons described, is using it as an antidepressant. With significant constraints on the findings, the current generally accepted understanding is that St. John’s wort is particularly helpful for mild-to-moderate depression. For major depression, it seems to be as effective as many prescription medications, but with fewer side effects.

Reported adverse side effects vary, especially depending on whether the concoction is ingested or applied to skin. Examples, not all confirmed or necessarily due to St. John’s Wort, are aggression, anxiety, diarrhea, dizziness, forgetfulness, insomnia, mental health conditions, restlessness, panic attacks, sensitivity to sunlight, and vomiting.

More certain are interactions with prescription medications for depression. Individual case reports attribute tiredness, nausea, confusion, and other neurological effects.

St. John’s Wort also interacts with a wide diversity of other medications, such as anticoagulants and those used for heart conditions. Some of the adverse reactions mirror those from the medications that St. John’s Wort is meant to replace or complement. Professional health advice is essential, emphasizing that people respond differently. It will always be a balance between an individual dealing with their own depression and dealing with their own side effects to different treatment or control approaches—while considering what preventive measures might be feasible.

Despite all the uncertainties, apparent side effects, and lack of evidence, various possible health applications for St. John’s Wort cannot be entirely dismissed, even when not accepted by scientists and health professionals. Science has not investigated all uses systemically for all people under all conditions. If it works or seems to work without leading to any harm, then it could be considered with caution. Psychosomatic health improvements are still health improvements, provided underlying conditions and causes are not masked, provided people still make lifestyle choices to prevent problems and to be healthier, and provided adverse consequences are absent.

It is the usual, obvious advice that we too  often ignore: For health, consult a health professional. Websites and news articles can direct queries and suggest questions, but they should never substitute for qualified and regulated health experts. People who benefit from St. John’s Wort might then indeed celebrate better health on June 24!

Scientific studies in this article in order:

Analyzing supplements:

Irritable Bowel Syndrome:


Medication interactions:

Individual case report:

This article originally appeared in the June 2024 issue of The Norwegian American.

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Ilan Kelman

Ilan Kelman is Professor of Disasters and Health at University College London, England, and Professor II at the University of Agder, Norway. His overall research interest is linking disasters and health, including the integration of climate change into disaster research and health research. Follow him at and @ILANKELMAN on Twitter and Instagram.