St John's wort
One of the few herbal products that works for depression in trials. We still never recommend it, because it makes many important medicines stop working.
At a glance
| Our verdict | Works for depression, but clashes with the pill, warfarin, blood thinners, transplant drugs and many others. |
| Sold for | Low mood |
| How sure the evidence is | Moderate that it works |
| Cost a month | About $15 |
Written for adults in Canada. It explains the evidence; it is not advice for you personally. Last reviewed 20 October 2026.
Supplement Check
Is it right for you?
St John's wort can stop the pill, blood thinners, transplant medicines and antidepressants working. If you take it with any of them, your check flags it to Dr. French the same day. Our Supplement Check looks at:
- Anyone taking a medicine in the table, or any other regular prescription medicine, unless a doctor or pharmacist has checked it
- Low mood most days, or any thoughts of harming yourself: see a doctor first
- Under 18: outside the Supplement Check, which is for adults
- Every medicine you take
Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.
$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check
What it is
St John's wort is a flowering plant, Hypericum perforatum, sold as a herbal extract for low mood.
How it acts
Our review did not cover how it acts on mood. What matters most is its effect on the liver and gut: it strongly switches on (induces) the enzymes CYP3A4, CYP2C9 and CYP1A2 and the drug pump P-glycoprotein, which clear many medicines from the body.
What it is used for, and what the evidence says
| Use | What the trials found | How sure we are |
|---|---|---|
| Major depression, against placebo | A Cochrane review found St John's wort better than placebo. [1] Trials from German-speaking countries were more favourable than trials from elsewhere, which lowers our confidence in the size of the effect. | Moderate |
| Major depression, against antidepressants | Similar to standard antidepressants, with fewer side effects. [1] | Moderate |
How sure we are: High means further research is very unlikely to change the answer; Moderate, it might; Low, it may well change; Very low, we are very unsure. These follow the GRADE method that guideline panels use.
Benefits
- Depression: better than placebo and similar to antidepressants, moderate certainty. [1]
- Fewer side effects than antidepressants in the trials. [1]
Risks and side effects
- Other medicines stop working. It lowers the levels of the contraceptive pill, blood thinners, transplant medicines, HIV medicines, antidepressants and many others (see the table).
- Serotonin syndrome when combined with antidepressants.
Interactions with medicines
This is why we never recommend it. St John's wort is a strong inducer: it speeds up the liver enzymes CYP3A4, CYP2C9 and CYP1A2 and the drug pump P-glycoprotein, so many medicines are cleared faster and stop working.
The list is not complete: many other medicines are cleared by the same enzymes.
| Medicine | What can happen | What to do |
|---|---|---|
| Hormonal contraceptives (the pill and others) | Lower levels; the contraceptive can fail | Do not take; Dr. French told the same day |
| Warfarin | Changes warfarin's effect | Do not take; Dr. French told the same day |
| Apixaban, rivaroxaban, edoxaban, dabigatran | Lower levels; less protection against clots | Do not take; Dr. French told the same day |
| Ciclosporin, tacrolimus (transplant medicines) | Lower levels; the medicine can fail | Do not take; Dr. French told the same day |
| Antidepressants | Lower antidepressant levels, and serotonin syndrome | Do not take; Dr. French told the same day |
| HIV medicines | Lower levels; the medicine can fail | Do not take; discuss with your doctor |
Who should not take it
- Anyone taking a medicine in the table, or any other regular prescription medicine, unless a doctor or pharmacist has checked it.
- Low mood most days, or any thoughts of harming yourself: see a doctor first. If you are thinking about suicide, call or text 9-8-8 (Suicide Crisis Helpline) now, any time; in immediate danger call 9-1-1.
- Under 18: outside the Supplement Check, which is for adults.
Dose and timing
We do not recommend a dose, and our review did not record the doses used in trials.
If you take it now, tell your doctor and pharmacist before any new medicine is started.
What we know about Canadians
No Canadian data on St John's wort use in our review.
Low mood is common in Canada. In 2022, 7.6% of Canadians aged 15 and older had a major depressive episode in the past year and 5.2% had generalised anxiety disorder, up from 4.7% and 2.6% in 2012. The rise was steepest in young women aged 15 to 24, in whom generalised anxiety tripled and depression doubled. Fewer than half (48.8%) of people with a disorder spoke to a health professional about it in the past year. [2]
Most at risk: women aged 15 to 24, unemployed people, and people who use substances (half of whom also have a mood or anxiety disorder). [3]
How sure are we: high. Statistics Canada Mental Health and Access to Care Survey 2022, a national survey with a structured diagnostic interview; nothing on St John's wort itself.
An honest comparison: low mood
Same outcome (depressive symptoms), cost a month in Canadian dollars. Exercise trials cannot be blinded, so their effects include expectation; supplement and medicine trials are placebo-controlled. Read the certainty column before comparing sizes.
| Option | Effect | How sure we are | Cost a month (CAD) |
|---|---|---|---|
| St John's wort | Better than placebo, similar to antidepressants, fewer side effects [1] | Moderate | About $15 |
| Walking or jogging, hard enough to breathe hard | About 3 points lower than control groups on the 27-point depression questionnaire (PHQ-9); 218 trials, 14,170 people [4] | Low | $0 |
| Strength training or yoga | About as much as walking (effect size about 0.5) [4] | Very low | $0 to $21 (classes cost more) |
| Mediterranean-style eating with a dietitian | 32% recovered against 8% in one small 12-week trial of 67 people [5] | Low | About $30 |
| SSRI antidepressant (sertraline or escitalopram, generic) | 1.75 points more than placebo on the clinician-rated Hamilton depression scale; about 15% have a large response to the drug itself; [6] all 21 antidepressants studied did better than placebo [7] | Moderate | $8 to $12 |
Read honestly: St John's wort is the one supplement here with evidence close to a medicine's. We still never recommend it, because it makes so many other medicines fail. A generic antidepressant costs about the same, and a doctor can check it against everything else you take.
Why we don't recommend it
St John's wort works for depression in trials, but we do not sell it and our check never recommends it, because it lowers the levels of the contraceptive pill, blood thinners, transplant and HIV medicines, antidepressants and many others.
Already taking it? If you also take an antidepressant, a hormonal contraceptive, warfarin, another blood thinner or a transplant medicine, your check flags this to Dr. French the same day; tell your doctor now. If your mood is low most days, a doctor's assessment comes first; if you have thoughts of harming yourself, call or text 9-8-8 now, any time.
This is not a verdict on whether it works: the trials say it does, with moderate certainty. It is a verdict on safety. St John's wort strongly speeds up the liver enzymes and the drug pump that clear many medicines, so it makes the pill, blood thinners and transplant drugs fail, and with antidepressants it can cause serotonin syndrome. Dr. French's approved rules keep it on the never-recommended list (20 October 2026), including for anyone whose mood questionnaire shows depression. Exercise and, when needed, a prescribed antidepressant chosen against your other medicines do the same job more safely.
Supplement Check
Before you buy it, get it checked
St John's wort can stop the pill, blood thinners, transplant medicines and antidepressants working. If you take it with any of them, your check flags it to Dr. French the same day. Our Supplement Check looks at:
- Anyone taking a medicine in the table, or any other regular prescription medicine, unless a doctor or pharmacist has checked it
- Low mood most days, or any thoughts of harming yourself: see a doctor first
- Under 18: outside the Supplement Check, which is for adults
- Every medicine you take
Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.
$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check
Disclosure of financial interest
White Pine Medical earns money from products bought through our Fullscript dispensary. Dr. French's Code of Ethics requires him to tell you this. You do not have to buy anything from us: every product is named by its ingredient and dose so you can buy it at any pharmacy, and the advice is the same wherever you buy it, or if you buy nothing.
References
- Linde K, Berner MM, Kriston L. St John's wort for major depression. Cochrane Database Syst Rev. 2008;(4):CD000448. doi:10.1002/14651858.CD000448.pub3. PMID 18843608.
- Statistics Canada. The Daily, 22 Sep 2023: Mental Health and Access to Care Survey, 2022. https://www150.statcan.gc.ca/n1/daily-quotidien/230922/dq230922b-eng.htm
- Halladay J, Ji C, Georgiades K, Slade T, Chapman C, Sunderland M, et al. Co-occurring mood, anxiety, and substance use disorders in Canada 2022: prevalence, patterns, correlates, and changes over time. Psychiatry Res. 2026;365:117370. doi:10.1016/j.psychres.2026.117370. PMID 42603524.
- Noetel M, Sanders T, Gallardo-Gómez D, Taylor P, del Pozo Cruz B, van den Hoek D, et al. Effect of exercise for depression: systematic review and network meta-analysis of randomised controlled trials. BMJ. 2024;384:e075847. doi:10.1136/bmj-2023-075847. PMID 38355154.
- Jacka FN, O'Neil A, Opie R, Itsiopoulos C, Cotton S, Mohebbi M, et al. A randomised controlled trial of dietary improvement for adults with major depression (the 'SMILES' trial). BMC Med. 2017;15(1):23. doi:10.1186/s12916-017-0791-y. PMID 28137247.
- Stone MB, Yaseen ZS, Miller BJ, Richardville K, Kalaria SN, Kirsch I. Response to acute monotherapy for major depressive disorder in randomized, placebo controlled trials submitted to the US Food and Drug Administration: individual participant data analysis. BMJ. 2022;378:e067606. doi:10.1136/bmj-2021-067606. PMID 35918097.
- Cipriani A, Furukawa TA, Salanti G, Chaimani A, Atkinson LZ, Ogawa Y, et al. Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder: a systematic review and network meta-analysis. Lancet. 2018;391(10128):1357-66. doi:10.1016/S0140-6736(17)32802-7. PMID 29477251.
Costs marked as estimates are typical Canadian retail or pharmacy prices, before any drug plan. Certainty grades are ours unless the review gave its own.