St. John’s wort is an herbal supplement that people may use to help reduce symptoms of depression, menopause, and certain skin conditions. But more research is necessary and it may cause a range of side effects.

Derived from a flowering plant known as Hypericum perforatum, St. John’s wort is a herb people commonly use as a part of alternative medicine to treat depression, anxiety, and attention deficit hyperactivity (ADHD).

It also appears to have antibacterial properties and may act as an antiviral agent.

The plant contains hypericin, a chemical that may be responsible for most of the herb’s efficacy. Other ingredients such as hyperforin and flavonoids may play a role.

Though its exact mechanism is unclear, the herb may act similarly to certain types of antidepressants by increasing the availability of neurotransmitters like dopamine, serotonin, and norepinephrine in the brain.

This article discusses the benefits of St. John’s wort, the best ways to use it, as well as potential side effects and risks.

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People most commonly use st. John’s wort to treat depression naturally.

In fact, a 2017 review found that St. John’s wort may be as effective as selective serotonin reuptake inhibitors (SSRIs), which are a class of antidepressants, at reducing symptoms of mild-to-moderate depression over a period of 4-12 weeks.

Additionally, a 2016 review of studies concluded that St. John’s wort was more effective than a placebo at treating mild or moderate depression.

Researchers cautioned, however, that there is a lack of research into the use of the herb to treat severe depression. In addition, the available research may not have properly accounted for possible adverse events.

In addition, research shows st. John’s wort may help with the symptoms of several other conditions, including:

  • ADHD: One small study conducted in 2010 showed that St. John’s wort might be “slightly effective” in treating ADHD. However, a 2020 report published by the American Academy of Family Physicians indicates that physicians do not recommend using St. John’s wort to treat ADHD until more evidence supports its use.
  • Atopic dermatitis: While one pilot study reported that applying St. John’s wort topically could improve symptoms of eczema compared to a placebo, researchers note that a person should treat these results with caution.
  • Psoriasis: According to one small study on 20 people with plaque-type psoriasis, applying St. John’s wort topically improved inflammation and decreased psoriasis severity. However, more research is needed.
  • Menopause: Some research suggests that St. John’s wort could help reduce symptoms associated with menopause, including hot flashes and depression.

Though people often use st. John’s wort to treat other issues like anxiety or seasonal affective disorder, the research on its effectiveness for these conditions is limited.

St. John’s wort may cause several side effects, including:

  • anxiety
  • dizziness
  • dry mouth
  • headache
  • light sensitivity
  • restlessness
  • sedation
  • sexual dysfunction
  • skin reactions
  • stomach upset
  • tiredness or fatigue

It may take several weeks to experience any benefit. Like antidepressants, a person should stop using St. John’s wort gradually to prevent side effects.

Taking St. John’s wort may come with some risks. Certain groups of people may need to limit or avoid the consumption of this herb. They include:

People taking medications

People should not take St. John’s wort if they are taking any of the following medications, as its use may make these medications less effective:

St. John’s wort may also increase the effect of SSRI antidepressants. This can lead to a hazardous increase in serotonin in the body, which can cause symptoms such as:

  • tremor
  • diarrhea
  • confusion
  • muscle stiffness
  • low body temperature

Also known as serotonin syndrome, this condition can even be fatal.

In addition, St. John’s wort can add to the effect of triptan drugs used for migraine, such as sumatriptan.

Research published in 2015 has also suggested that St. John’s wort has a similar profile to fluoxetine and can produce the same adverse reactions. Serious adverse effects could occur if the two drugs are taken together.

People with certain mood disorders

A person with a diagnosis of depression should not use St. John’s wort as an alternative to therapies recommended by a doctor. If the herb is not effective, the depression may worsen.

In some cases, St. John’s wort can trigger psychosis. This is another reason people with major depression or bipolar disorder should be careful with the herb despite its potential benefits in this area. It may cause a person to develop a manic episode.

Pregnancy and nursing

It is not yet clear whether St. John’s wort is safe to use while pregnant, or while breastfeeding or chestfeeding.

One 2022 study seems to indicate it may be safe during pregnancy. However, the National Center for Complementary and Integrative Health (NCCIH) warns that it has been shown to cause birth defects in animal studies.

In addition, nursing people should know that St. John’s wort can get into breast milk and may cause babies to become fussy, drowsy, or experience colic.

People should always discuss with a doctor before taking St. John’s wort, other supplements, or alternative therapies.

Most people take St. John’s wort either in tablet or capsule form, but they can also consume it by brewing special teabags. For topical application, a person can get a tincture, which is a medicinal extract in a solution of alcohol.

For adults, the usual dose in capsule or dry tablet form is 300 milligrams (mg) three times a day, which a person should take with meals or as directed by a healthcare professional.

Do I need a prescription?

In the United States, the Food and Drug Administration (FDA) considers St. John’s wort a dietary supplement and does not approve it for use as a medication.

Therefore, St. John’s wort is available over-the-counter in the U.S. and in many other countries. In some countries such as Ireland, however, a person needs a prescription to get it.

Here are a few common questions about St. John’s wort.

How does St. John’s wort make you feel?

St. John’s wort may help ease symptoms of depression in some people by altering levels of certain neurotransmitters in the brain.

However, it can cause negative side effects in other cases, including anxiety, stomach upset, headache, dizziness, and fatigue.

Can St John’s wort cause weight gain?

There is no evidence to suggest that St. John’s wort causes weight gain directly.

Still, a person might experience weight loss or weight gain after taking St. John’s wort. This is because it could help improve symptoms of depression, a condition often associated with appetite and body weight changes.

What should you avoid when taking St. John’s wort?

St. John’s wort can interact with several medications, including antidepressants, oral contraceptives, warfarin, and certain types of medications for heart disease, cancer, and HIV.

If a person is taking any of these medications, it’s important to talk with a doctor before taking St. John’s wort to prevent adverse effects.

A person can easily purchase st. John’s wort is over-the-counter and can also find it as an ingredient in many teas, tablets, capsules, and topical ointments.

This herb is a common ingredient used in alternative medication to treat various conditions, though not enough research exists to back up all of its uses.

In addition, St. John’s wort can interact with some prescription drugs and cause several adverse side effects for people who have certain mood disorders. It may also negatively affect unborn or nursing babies.

A person should be careful and consult with a healthcare professional before using it.