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Everything you need to know about St. John’s wort

St. John’s wort is a plant with yellow flowers that grows in a range of climates in the United States and Europe. Also known as hypericum perforatum or klamath weed, ancient Greeks used the plant to treat a range of ailments, from animal bites to depression. Its modern-day benefits fall within similar realms, but its scientific efficacy and safety remain largely unproven within the medical community. The potential side effects aren’t widely understood.

St. John’s wort primarily works through hypericin and hyperforin, the two biologically active compounds in the supplement that have been shown to have significant medical properties. “As in any plant, there are many other chemicals present, including flavonoids (quercetin, rutin, luteolin) and tannins, which may have independent health benefits,” says Harrison Weed, MD, an internal medicine physician at The Ohio State University Wexner Medical Center.

What does St. John’s wort do? Uses and benefits

St. John’s wort is a natural remedy often sold in tablet or capsule format or as an ingredient in a variety of wellness supplements and teas. The most common ailments St. John’s wort treats are:

  • Mild depression
  • Menopausal symptoms
  • Inflammatory diseases
  • Minor cuts and burns

As a supplement, it’s not regulated by the U.S. Food and Drug Administration (FDA) or approved to treat any of these conditions. Though, there is some research indicating its effectiveness.

Mild depression

Of the known usages for St. John’s wort, depression is the most widely studied and the most commonly cited. “Patients with mild depression have been shown to benefit significantly more than placebo and [St. John’s wort is] as effective as standard antidepressants,” says Erin Nance, MD, a New York City–based orthopedic surgeon, citing the Cochrane Review’s systematic review on the subject, which is considered to be one of the most comprehensive. While the clinical trials for treating mild depression indicate positive results, when it comes to treating moderate depression, major depressive disorder, severe depression, or bipolar disorder, St. John’s wort is not a recommended treatment.

The hyperforin found in St. John’s wort acts on chemical messengers in the brain that can affect mood to treat mild depression, similar to the way selective serotonin reuptake inhibitors (SSRIs) work. “Hypericin used to be thought of as the active ingredient with regard to treating depression,” explains Dr. Weed. “Currently it is thought that hyperforin is the active ingredient through effects on neurotransmitters in the brain similar to the effects of prescription antidepressants.”

Menopausal symptoms

When it comes to treating menopausal symptoms, the herbal supplement has been demonstrated to be effective at treating psychological symptoms related to menopause, such as sadness, anxiety, and stress, as well as physical symptoms such as hot flashes and night sweats. While the findings are statistically significant when St. John’s wort is taken alone, when taken alongside black cohosh, a flowering herb, the research is even more compelling.

St. John’s wort’s ability to treat psychological menopausal symptoms is thought to act similarly to its ability to treat mild depression and seasonal affective disorder, while its effects on physical symptoms such as hot flashes are less widely studied and understood. Because of the way St. John’s wort affects the brain’s serotonin levels, it may also be effective in treating premenstrual syndrome. 

Inflammatory diseases

While this application of St. John’s wort is not as widely studied as others, the supplement has been shown to act as an anti-inflammatory agent in mice and rats by limiting the expression of inflammatory agents in the body. 

A concert of extracts from St. John’s wort extract work together to decrease the activity of or decrease the production of certain inflammatory agents. 

Minor cuts and burns

According to Dr. Nance, the herbal supplement is also sometimes used as an antibacterial treatment for minor cuts and burns. While there are plenty of topical St. John’s wort products on the market, studies indicate that oral formulations have a more positive impact on wound healing than topical treatments containing St. John’s wort.

St. John’s wort is believed to be successful in treating small wounds due to hyperforin, the main antibacterial component in the herbal supplement. Hyperforin acts to slow the growth of certain types of microorganisms that are present within cuts and wounds. Further studies indicate that the hypericin in St. John’s wort could be effective in inactivating certain types of viruses.


A common St. John’s wort dosage ranges from 300 mg to 900 mg a day taken in divided doses. It’s important to consult your doctor about the right dosage for you; he or she will consider other medications you are taking and your medical history. St. John’s wort is classified as a dietary supplement, meaning it, like other natural medicines, is not monitored by the FDA. It’s important to do some research to find a quality product to treat your condition. Try to avoid purchasing the supplement from another country when buying online.

When taking St. John’s wort to treat mild symptoms of depression, allow a few weeks for the hyperforin within the supplement to have an effect on neurotransmitters, similar to prescription antidepressant drugs. “It usually takes a few weeks for neurotransmitter-altering medications to have an impact on mood,” says Weed. Also, like any antidepressant, when you stop taking St. John’s wort, you should taper it slowly, rather than abruptly stopping it. Your healthcare provider can advise you on an appropriate tapering schedule. 

The long-term effects of St. John’s wort are less widely studied. Because of this, most health experts will recommend limiting its use to no more than six months. “Because there are many different compounds in St. John’s wort, each with its own half-life, and because the metabolism of each person is different, one should probably assume that the effects of St. John’s wort ‘stay’ in a person’s ‘system’ for a few weeks,” Dr. Weed adds.

St. John’s wort side effects

The most common side effects of taking St. John’s wort include:

  • Abdominal bloating
  • Anorgasmia (difficulty reaching orgasm)
  • Constipation
  • Dizziness/confusion
  • Dry mouth
  • Headache 
  • Hypertension (increased blood pressure)
  • Nausea
  • Photosensitivity (skin redness/rash/burn with sun exposure)
  • Tiredness/sedation
  • Urinary frequency (increased)
  • Vivid dreams

In addition to these adverse reactions, St. John’s wort can cause a life-threatening reaction, called serotonin syndrome, when taken with some medications. Serotonin syndrome can occur due to the buildup of too much serotonin. Its symptoms include: agitation, hyperthermia (overheating), sweating, tachycardia (fast heartbeat), and neuromuscular disturbances, including rigidity. You should seek medical help immediately if you experience any of these symptoms.


Because St. John’s wort has so many interactions with over-the-counter and prescription drugs, it’s important to check with your healthcare provider to see if it’s safe for you. “St. John’s Wort is known to have interactions with multiple medications due to its effect on enzymatic breakdown of other medications,” says Dr. Nance. 

It’s crucial to have a conversation with your doctor or pharmacist before beginning a St. John’s wort regimen because of its potential for drug-drug interactions. Some medical professionals believe that the risks outweigh the potential benefits, including Dr. Weed. “Treatment failures caused by St. John’s wort have been reported for anticoagulation, HIV, fungal infections, glaucoma, transplanted organs, heart arrhythmias, and contraception,” he says. “The more you take, the more adverse the effects.”

The following drugs may not be as effective when taken with St. John’s wort:

The following drugs can cause life-threatening serotonin syndrome when taken with St. John’s wort:

  • Fluoxetine (Prozac)
  • Sertraline (Zoloft)
  • All selective serotonin reuptake inhibitor (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs)
  • Triptans (a class of medications used for migraine, such as Imitrex, or sumatriptan) 

When St. John’s wort is taken with fexofenadine (Allegra), it may cause buildup and intensify normal side effects.

The above list is not a comprehensive list of drug interactions, but provides some examples. Be sure to consult with your healthcare provider to ensure St. John’s wort is appropriate and safe to take with any other medications (prescription and over-the-counter, including other supplements) you currently use. 

3 considerations before taking St. John’s wort

St. John’s wort has been used for hundreds of years as an alternative medicine by a variety of cultures to treat ailments ranging from anxiety and depressive symptoms to wound and burn care. Determining whether the herbal medicine is right for you requires a few considerations.

  1. The condition you want to treat: St. John’s wort is most promising for treating mild depression, menopausal symptoms, and minor cuts and burns. Treating major depression or serious wounds requires a different approach than St. John’s wort. Additionally, it’s not commonly recommended to treat depression without a doctor’s involvement, so seek a medical opinion you respect before beginning your own St. John’s wort regimen for these purposes.
  2. How long you anticipate taking the supplement: Because long-term consequences of taking St. John’s wort aren’t widely studied, it’s recommended to treat conditions that can be resolved within six months
  3. Adverse effects and interactions: Consider the side effects and drug interactions of St. John’s wort before taking the herbal supplement. 

No matter how you’ll use it, never begin treatment with St. John’s wort without consulting a healthcare provider, as many serious interactions can occur.