St John’s wort

Research has found that St John's wort is useful in the treatment of mild to moderate depression, but not effective in severe depression.

In an analysis of studies comparing St John’s wort with a placebo (sugar pills) and standard antidepressants (SSRIs or tricyclics), the authors found that compared with placebo, people taking St John’s wort were more likely to have an improvement in their symptoms. There were no significant differences in depression response rates between St John’s wort and standard antidepressants. The studies also found that patients taking St John’s wort were less likely to drop out of trials due to adverse effects than those taking standard antidepressants.

There are a number of products available on the market containing St John's wort (Hypericum). When buying St John's wort you should be careful about the potency (strength) and purity of the product. A standardised extract of 0.3% Hypericum is mostly used in clinical trials.

St John's wort is possibly effective for menopausal symptoms, plaque psoriasis, wound healing and somatisation disorder. Read more about St John's wort(external link) National Institute of Health.  

St John’s wort can be taken as tablets and capsules. You can also get it as a tea, and as a liquid called a tincture, which you can take as drops in water. There are additional products available that combine St John's wort with other herbs, such as lemon balm (Melissa officianalis) and hops (Humulus lupulus).

• Because St John's wort is classified as a supplement, the strength and dose will vary depending on what brand of St John's wort you take. Always check the dosing instructions on the product label or packaging.
• The effect of St John's wort is not immediate. You may need to take it for two to three weeks before you notice any improvement. If there is no change in your symptoms by then, it’s likely St John's wort will not be of benefit for you and you should talk to your doctor about other ways of managing your symptoms.

You should not use St John's wort if you:

• are pregnant or planning a pregnancy
• are breastfeeding
• have bipolar disease
• are taking antidepressants such as SSRIs, such as paroxetine, citalopram, fluoxetine, sertraline or venlafaxine
• are taking triptan medication for migraine, such as sumatriptan, rizatriptan and zolmitriptan.

St John's wort interacts with a large number of medicines. In some cases, St. John's wort makes the medicines less effective and in other cases, it may make the effects of a medicine stronger, which can lead to more side effects.

Note: the above list is not complete. Check with your doctor or pharmacist before starting St John’s wort or before starting any new medicines.

Although St John’s wort is a herb, it is still an active treatment that has specific effects and it can cause side effects. Side effects from St John's wort may include:

• tummy upset
• skin rash, hives or other skin rashes
• feeling tired
• restlessness
• headache
• dry mouth
• feelings of dizziness or mental confusion.

Your skin can become more sensitive to sunlight. If you have light skin and are taking St John's wort, wear long sleeves and a hat when in the sun, and use a sunscreen with at least SPF15 or higher.

Risk of serotonin syndrome

Serotonin syndrome occurs when the level of serotonin in your brain gets too high. It can happen with the use of St John’s wort and some medicines such as SSRIs or the pain relief medication, tramadol.

• You are at risk of serotonin syndrome if you just started taking or increased the dose of your St John’s wort or if you are taking St John's wort with other medicines that also increase serotonin levels.
• Symptoms can range from mild, such as shivering and diarrhoea (runny poos), to severe, such as muscle rigidity, fever and seizures.
• Milder forms of serotonin syndrome may go away within a few days of stopping the medicines that caused your symptoms.
• Severe serotonin syndrome needs hospital admission and can be fatal if not treated.
• Read more about serotonin syndrome.

Withdrawal symptoms

Some people may get withdrawal symptoms when they stop taking St John’s wort abruptly, such as feeling sick, dizzy and feeling tense. As St John’s wort has similar properties to prescribed antidepressants, it is advisable to slowly reduce your dosage so as to lessen the chance of withdrawal symptoms, especially if you have been taking it for longer than a few weeks.

Read more about medicines and side effects and reporting a reaction you think might be a side effect.