Post Highlights

St John’s Wort effectiveness


St John’s Wort (Hypericum Perforatum) is a traditional herbal medicine with a long history of use for different conditions. Nowadays, St John’s Wort is actively used as an herbal supplement to help with symptoms of mild depression and anxiety. In this post, I am looking at St John’s Wort effectiveness and possible side effects associated with taking this herbal product.


Most commonly, St John’s Wort is available in tablet and capsule formulations, however other preparations of St John’s

Wort exist including herbal teas, powders, tinctures (liquid extract).

St John’s wort has been widely researched primarily to study its antidepressant properties as well as to investigate the interactions with other medications. One important message to ‘take home’ is that St John’s Wort can interact with many different medicines, having a huge impact on a patient’s treatment.

St John’s Wort Active Ingredients And Mechanism Of Action

St John’s Wort Active Ingredients And Mechanism Of Action

Two main active ingredients found in St John’s Wort are Hypericin and Hyperforin both believed to have antidepressant properties.

Animal studies with rats suggest actions on different receptors including upregulation (increase number) of serotonin receptors

which cause changes in the amounts of neurotransmitters in the areas of the brain associated with depression (Butterweck, 2003).

As many studies suggest fluctuations of serotonin, norepinephrine, and dopamine neurotransmitters in the central nervous system are associated with depression and currently available antidepressants act to increase one or more of those neurotransmitters in the brain (Moret & Briley, 2011).

St John’s Wort Effectiveness

St John’s Wort Effectiveness

Information from different small clinical trials suggests that St John’s Wort is not invariably effective for the treatment of depression (NIH, ND).

One clinical trial, for example, showed no difference (lack of efficacy) in the reduction of minor depression symptoms

between St John’s Wort and Citalopram a Selective Serotonin Reuptake Inhibitor (SSRI, a type of antidepressants) and placebo (a dummy pill).

On the other hand, another small clinical trial showed that St John’s Wort is as equally as effective as a placebo or SSRI antidepressant (Sertraline was used in this trial) in the treatment of moderate depression or may be more effective than placebo (ibid). SSRIs are the most commonly prescribed antidepressants in the UK.

However, the best evidence behind the effectiveness of St John’s Wort comes from a systemic review and meta-analysis (summary of results from a number of studies) which looked at a total of 66 studies with 15161 patients. Key findings in relation to the effectiveness of St John’s work from this meta and network analysis:

  • St John’s Wort is effective for the treatment of acute depression with a small difference when compared to placebo (a dummy pill).
  • Network analysis reports that St John’s Wort shows similar efficacy to selective serotonin reuptake inhibitors and tricyclic antidepressants with a better ‘acceptability’ than both classes of antidepressants
  • St Johns Wort has a high risk of negative interactions with other drugs

St John’s Wort Interaction With Drugs

Many drugs commonly used in the treatment of different conditions are metabolized (broken down) by liver enzymes such as those produced by the cytochrome P450 genes.

St John’s wort can induce (increase activity) of cytochrome p450 enzymes and by doing so it can reduce the concentration of drugs in the body, hence reducing their effectiveness.

Many Important Interactions Between St John`s Wort And Other Drugs Have Been Identified. Some Classes Of Drugs Affected Include:

  • Antidepressants (risk of serotonin syndrome)
  • Contraceptive pills (reduced efficacy, with unwanted pregnancies, reported (Henderson et al, 2002))
  • Anticoagulants like warfarin
  • HIV medications and many more

Always speak to a healthcare professional if you take different medication(s) and considering taking St John’s wort.

St John’s Wort Side Effects

Most People Who Take St John’ s Wort Do Not Experience Side Effects, However Possible Side Effects Include (eMC, ND):

  • Allergic reactions for example skin rash, red and itchy skin, hives
  • Upset stomach for example diarrhea or constipation, indigestion, feeling sick (nausea)
  • Fatigue
  • Headaches and dizziness
  • Sensitivity to light
  • Nerve pain, tingling, anxiety

St John’s Wort And NICE Recommendation

The official guide on the treatment of depression in adults (NICE) advises practitioners not to recommend St John’s Wort for the treatment of depression, despite evident benefits in the treatment of mild to moderate depression (NICE, 2009). This recommendation comes from a lack of information on appropriate doses, variations in preparations that are available on the market, and possible risk of side effects with other drugs.

In conclusion, St Johns Wort was shown to be effective in the management of depression symptoms with minor and uncommon side effects. One important aspect of taking St John’s Wort is the possible risk of interactions with other medications.
Anyone who experiences depression symptoms every day (most of the day) for more than 2 weeks should see their GP. Taking St John’s Wort should not substitute for seeing help from their doctor.