Herbs and Antidepressants: St. John's Wort, Serotonin Syndrome and Others
Why St. John's wort should not be combined with antidepressants without a clinician: serotonin syndrome signs first, what NCCIH, MedlinePlus and the NHS say, and where to get help.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Serotonin syndrome is a medical emergency. MedlinePlus calls it a potentially life-threatening reaction to certain medicines, and says untreated it can be deadly. [1] NCCIH says symptoms occur within minutes to hours and may include agitation, diarrhea, fast heartbeat, high blood pressure, hallucinations and increased body temperature. [2] MedlinePlus also lists loss of coordination, and says to contact your provider right away if you have symptoms. [1]
- Call 911 (US) if the person collapses, has a seizure, has trouble breathing or cannot be awakened. [3]
- Poison Help, 1-800-222-1222 (US), says its help is free, expert and confidential. [3]
- Do not stop a prescribed antidepressant on your own. MedlinePlus says, for medicines that can cause serotonin syndrome, not to stop taking your medicine, and to talk to your health care provider about your concerns first. [1]
- If you are in emotional crisis or thinking of harming yourself, call or text 988 (US). The 988 Lifeline says it is available 24/7/365 and conversations are free and confidential. [4] See mental health crisis and natural remedies.
What St. John's wort is, and what it is studied for
This section is research, not tradition. NCCIH says studies indicate St. John's wort may be helpful for mild or moderate depression. [6] The same page says the herb can interact with many medicines, so a possible benefit does not make it a safe add-on to an antidepressant. NCCIH adds that depression can be a serious illness and that you should consult a health care provider if you or someone in your family may have it. [6] See the herb profile St. John's wort and St. John's wort versus prescription antidepressants.Other medicines St. John's wort affects
Because the herb can weaken many medicines, it matters well beyond depression treatment. NCCIH lists birth control pills, cyclosporine, some seizure, heart, HIV and cancer medicines, warfarin and certain statins. [6] See how interactions happen and St. John's wort interactions.Limits
Most of this page rests on NCCIH, MedlinePlus, the NHS and one 2009 literature review. We did not read EMA/HMPC or Health Canada statements. Nothing here says that any one product is safe.Frequently asked questions
Can I take St. John's wort with an SSRI?
NCCIH says combining St. John's wort and certain antidepressants can lead to a potentially life-threatening increase in serotonin. [2] Talk to your prescriber or pharmacist before combining, and do not stop your antidepressant on your own. [1]
What are the signs of serotonin syndrome?
MedlinePlus lists agitation or restlessness, fast heartbeat and high blood pressure, increased body temperature and loss of coordination. [1] Contact your provider right away if you have symptoms. [1]
Is St. John's wort a natural alternative to antidepressants?
NCCIH says it may help mild or moderate depression, and that depression can be serious. [6] Switching medicines is a decision for you and your prescriber.
Do other herbs cause serotonin syndrome?
Proper evidence not found in the pages we read, as the table above explains. A pharmacist can check any specific product.
Where can I get help in a mental health crisis?
In the US, the 988 Lifeline is available by call, text or chat, 24/7. [4] Outside the US, use your local emergency and crisis services; we did not read a source listing crisis lines by country.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
What the sources say about interactions
| Combination | What the source found | Strength of evidence |
|---|---|---|
| St. John's wort with certain antidepressants or other serotonin-affecting drugs | Increased serotonin-related side effects, which can be serious. [6] A review lists serotonin syndrome or lethargy when it was given with serotonin reuptake inhibitors among its well-documented interactions. [8] | Documented (NCCIH statement and literature review) |
| St. John's wort weakening some antidepressants | NCCIH names amitriptyline and bupropion among antidepressants whose effects it can weaken. [6] | Documented (NCCIH statement) |
| Antidepressants with other medicines | The NHS says some antidepressants combined with alcohol, some foods or other medicines, including NSAIDs and other antidepressants, can cause side effects. [7] | NHS advice |
| Other single herbs | Proper evidence not found. We searched the NCCIH pages for ginkgo, garlic, green tea, turmeric, valerian, chamomile, echinacea, milk thistle, elderberry, ginger, saw palmetto, licorice, hawthorn, fenugreek and cinnamon (15 pages) for the word "serotonin" and found no mention. Only the St. John's wort pages mention it. | Not found in the pages we read; this is not proof that no other herb or supplement matters |
Serotonin syndrome most often occurs when two or more medicines or drugs that affect serotonin are taken together, MedlinePlus says. It is more likely when you first start a medicine or increase its dose. [1] Its examples are drug combinations such as triptans with SSRIs, and the page we read does not mention herbs, so ask a pharmacist about any supplement that claims to affect mood or serotonin. Our safety pages on serotonin syndrome and other medicine reaction signs and supplements and antidepressants cover supplements beyond herbs.
Pregnancy, breastfeeding and children
References
- MedlinePlus Medical Encyclopedia, Serotonin syndrome. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NCCIH, US), St. John's Wort and Depression: In Depth, last updated December 2017 (older page). Read 2026-10-23.
- Poison Control (National Capital Poison Center, US), poison.org. Read 2026-10-23.
- 988 Suicide & Crisis Lifeline (US), 988lifeline.org. Read 2026-10-23.
- GBIF Secretariat, GBIF Backbone Taxonomy match for Hypericum perforatum: accepted name Hypericum perforatum L.. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NCCIH, US), St. John's Wort, last updated May 2025. Read 2026-10-23.
- NHS (UK), Antidepressants, page last reviewed 12 June 2025. Read 2026-10-23.
- Borrelli F, Izzo AA. Herb-drug interactions with St John's wort (Hypericum perforatum): an update on clinical observations. AAPS Journal 2009; PubMed abstract. Read 2026-10-23.