Herbal Supplements for Mental Health: What the Evidence Actually Says
Walk into any health shop and you will find a shelf of herbal capsules promising calmer nerves, better sleep and a lifted mood. Some of these herbs do have real research behind them. Many do not, and a few carry risks that rarely make it onto the front of the box. This guide sorts the promising from the overhyped, and it does so honestly — because when the subject is your mental health, being told the truth matters more than being sold a tidy list of ten miracle plants.
Two things are worth saying plainly before we go any further. First, herbal supplements are not a replacement for professional mental health care. For anything beyond mild, short-lived symptoms, the right first step is a conversation with your GP, not a supplement aisle. Second, “natural” does not mean “harmless” — some of the best-studied herbs here interact dangerously with prescription medicines. Keep both in mind as you read.
How to use this guide: treat it as background reading, not a treatment plan. Before trying any herb, especially if you take other medicines, are pregnant, or have an existing health condition, speak to a pharmacist or GP. They can check for interactions in minutes — a step no article can do for you.
A word on evidence and UK regulation
Most herbal products sold in the UK are food supplements or traditional herbal medicines, not licensed medicines. That distinction matters. Under the Medicines and Healthcare products Regulatory Agency (MHRA), a product carrying a Traditional Herbal Registration (THR) mark has met standards for quality, safety and manufacturing — but its permitted claims are based on long-standing traditional use, not on proof that it works. In other words, the THR mark tells you the product is made to a decent standard; it does not tell you it will help.
The NHS is candid on this point: evidence for the effectiveness of herbal medicines is generally very limited, and their use is often based on tradition rather than science. Herbal remedies are also no longer prescribed on the NHS, because the evidence base is not strong enough to justify it. None of that means these herbs are useless — some genuinely help some people — but it does mean a healthy scepticism is the right starting posture. If you do experience a side effect from a herbal product, you can report it through the MHRA’s Yellow Card Scheme, which helps regulators spot emerging safety signals.
The herbs with the most promising evidence
These four have the strongest research base for mood, stress and anxiety. “Strongest” is relative — even here, trials are often short and preparations vary — but this is where the science is most encouraging.
Lavender oil (Silexan) — for anxiety
Of all the herbs in this article, a standardised oral lavender oil preparation known as Silexan arguably has the most robust evidence. Pooled analyses of several randomised, placebo-controlled trials, involving well over a thousand patients, found that an 80 mg daily dose meaningfully reduced anxiety scores over roughly ten weeks in people with subthreshold anxiety and generalised anxiety disorder, and it was generally well tolerated. It is licensed as a medicine in Germany and some other countries. The most common side effect is mild — a lavender-scented burp. Even so, this is anxiety in a research setting with a specific preparation, not a licence to self-treat a diagnosed anxiety disorder without guidance.
St John’s wort — for mild-to-moderate depression
St John’s wort (Hypericum perforatum) is the most-studied herb for low mood, and the evidence is real: systematic reviews suggest it can outperform placebo and, in some trials, works about as well as standard antidepressants for mild-to-moderate depression. But three caveats are essential. It does not appear to help severe depression. The evidence for anxiety and seasonal affective disorder is weak. And — this is the big one — it has serious, well-documented interactions with many prescription medicines. More on that in the safety section below, because it genuinely matters.
Saffron — for low mood
Saffron, the spice, has a small but growing body of trials for depressive symptoms. Randomised, placebo-controlled studies have reported improvements in mood in people with low mood or mild-to-moderate depression, and an international task force of mood-disorder specialists judged the directional evidence for saffron in depression to be positive. At the modest doses used in supplements it appears well tolerated, though very high doses are unsafe and should be avoided, particularly in pregnancy. It remains an emerging option rather than an established one.
Ashwagandha — for stress and anxiety
Ashwagandha (Withania somnifera), an adaptogenic herb from Ayurvedic medicine, has attracted a wave of recent trials. Several 2024 and 2025 meta-analyses found that standardised root extracts reliably lower the stress hormone cortisol, and a number report reductions in perceived stress and anxiety. The picture is not uniform, though — at least one recent analysis found a clear drop in cortisol but no significant change in how stressed people actually felt. So the honest summary is “promising but mixed”. Trials typically use standardised extracts in the region of a few hundred milligrams a day. Safety-wise it is generally well tolerated short-term, but there have been rare reports of liver injury, it is not recommended in pregnancy, and people with thyroid or autoimmune conditions should take advice first.
Traditional herbs with lighter evidence
These are widely sold and long used, but the research is thinner or more mixed. That does not make them worthless; it means expectations should be modest and claims taken with a pinch of salt.
Chamomile
A gentle, familiar herb, usually taken as tea. A handful of trials suggest it may take the edge off mild anxiety symptoms, but the evidence is limited. Its safety record is reassuring for most people, though those allergic to plants in the daisy family should be cautious.
Lemon balm
Traditionally used for restlessness and mild anxiety, sometimes alongside other calming herbs. Small studies hint at a soothing effect, but robust, large-scale trials are lacking.
Valerian
Best known as a sleep aid, valerian is also used for anxiety. The evidence for sleep is genuinely mixed — some people find it helpful, trials are inconsistent — and for anxiety it is weaker still. It can cause drowsiness, so it does not mix well with alcohol or sedatives.
Passionflower and rhodiola
Passionflower is a traditional remedy for nervous tension with only preliminary supporting evidence. Rhodiola, another adaptogen, is used for stress and fatigue, again on a limited research base. Both are reasonable to be curious about and unwise to rely on.
Evidence at a glance
The table below is a quick reference, not a ranking of what will work for you. “Evidence” here reflects the current weight of research, which continues to evolve.
| Herb | Most-studied use | Evidence |
|---|---|---|
| Lavender (Silexan) | Anxiety symptoms | Reasonable (RCTs) |
| St John’s wort | Mild-to-moderate depression | Moderate; major interactions |
| Saffron | Low mood | Emerging, positive |
| Ashwagandha | Stress, anxiety | Mixed but promising |
| Chamomile, valerian, lemon balm | Mild anxiety, sleep | Limited |
Visually, the relative weight of evidence looks something like this — a useful reminder that “popular” and “proven” are not the same thing.
Relative strength of the current evidence (illustrative)
Lavender (Silexan) — anxiety
St John’s wort — mild-to-moderate depression
Saffron — low mood
Ashwagandha — stress and anxiety
Chamomile, valerian, lemon balm, passionflower
Illustrative only. Trial quality, preparation and dose all vary, and evidence changes as new studies appear.
Safety, interactions and who should be cautious
This is the section most listicles skip, and it is the most important one. Herbal supplements are biologically active — that is the whole point — which means they can interact with medicines and are not right for everyone.
The St John’s wort interaction problem
St John’s wort is a striking example of why “natural” is not the same as “safe”. It speeds up the liver enzymes that clear many drugs from the body, which can make those medicines less effective, and it can dangerously add to the effects of others. The panel below lists some of the interactions regulators and researchers have flagged. If you take any prescription medicine, do not start St John’s wort without checking with a pharmacist or GP first.
St John’s wort can interfere with, among others:
Antidepressants such as SSRIs — risk of serotonin syndrome, a potentially serious reaction. Hormonal contraceptives — the UK regulator has warned it can reduce their effectiveness, with reported unplanned pregnancies. Warfarin and other anticoagulants. Anti-epileptic medicines. Immunosuppressants used after transplants, such as ciclosporin and tacrolimus. Some HIV and cancer medicines, digoxin, and certain statins. This is not a complete list — which is exactly why a pharmacist check is non-negotiable.
Pregnancy, breastfeeding, conditions and surgery
As a general rule, herbal supplements are best avoided in pregnancy and breastfeeding unless a professional says otherwise, because safety data is often lacking. If you have a long-term condition — liver, kidney, thyroid, heart or a mental health diagnosis you are being treated for — check before adding a herb. And tell your doctor about any herbal products before an operation, as some affect bleeding, blood pressure or anaesthesia; you may be advised to stop them beforehand.
Buying safely
Look for the THR mark and an MHRA product code on the packaging. Be wary of buying herbal supplements from unfamiliar websites or overseas sellers: products bought this way are more likely to be poor quality, contaminated, or spiked with undeclared pharmaceutical ingredients. Slimming and “sexual performance” herbal products are particular offenders and are best avoided altogether.
Where herbs fit alongside proven approaches
It helps to keep herbal supplements in perspective. The interventions with the strongest evidence for mental health are not sold in capsules: regular physical activity, decent sleep, social connection, and — where needed — talking therapies and medication prescribed and monitored by professionals. Herbs, at best, sit around the edges of that picture as a possible support for mild symptoms, not the foundation.
Nutrition belongs in that foundation too. A diet that keeps blood sugar steady and covers key nutrients supports mood and energy, and genuine deficiencies in nutrients such as vitamin D, B12 or iron can affect how you feel. If you suspect a shortfall, structured assessment such as micronutrient testing is a more sensible route than guessing with a cupboard full of supplements.
When to seek professional help
Please treat this as the most important takeaway of the article. If low mood, anxiety or stress is affecting your daily life, lasting more than a couple of weeks, or getting worse, speak to your GP. Herbal supplements are not a substitute for that conversation, and delaying proper support to try remedies on your own can allow a treatable problem to deepen.
If you would like tailored advice on the nutrition side of things, our guide to finding a qualified nutritionist is a useful starting point, and you can read more about our approach on the about page. In the UK, if you need to talk to someone urgently you can call NHS 111 and choose the mental health option, or contact Samaritans free, at any time, on 116 123. If you or someone else is in immediate danger, call 999.
The bottom line: a few herbs — lavender for anxiety, St John’s wort and saffron for low mood, ashwagandha for stress — have encouraging but imperfect evidence, while most others rest largely on tradition. None is a cure, none replaces professional care, and some interact with medicines in ways that can cause real harm. Used thoughtfully, with a pharmacist’s input and alongside the basics of sleep, movement, connection and good food, they may play a small supporting role. That is a realistic promise, and a more trustworthy one than the usual list of miracles.
This article is general information about mental health and wellbeing and is written for educational purposes. It is a sensitive subject, and if you are struggling personally, the support routes above are there for you. It does not constitute medical advice, and no herbal supplement should be started or stopped without professional guidance.
References and Citations
- NHS. Herbal medicines. Available at: https://www.nhs.uk/conditions/herbal-medicines/
- Medicines and Healthcare products Regulatory Agency (GOV.UK). Apply for a Traditional Herbal Registration (THR); Herbal medicines granted a THR. Available at: https://www.gov.uk/guidance/apply-for-a-traditional-herbal-registration-thr
- National Center for Complementary and Integrative Health (NCCIH). St. John’s Wort and Depression: In Depth. Available at: https://www.nccih.nih.gov/health/st-johns-wort-and-depression-in-depth
- Nicolussi, S., et al. (2020). Clinical relevance of St. John’s wort drug interactions revisited. British Journal of Pharmacology / PMC. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC7056460/
- Mind. St John’s wort (information sheet). Available at: https://www.mind.org.uk/information-support/drugs-and-treatments/complementary-and-alternative-therapies/
- Kasper, S., et al. (2023). Efficacy of Silexan in patients with anxiety disorders: a meta-analysis of randomised, placebo-controlled trials. European Archives of Psychiatry and Clinical Neuroscience / PMC. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10465640/
- Bachour, G., et al. (2025). Effects of ashwagandha supplements on cortisol, stress and anxiety levels in adults: a systematic review and meta-analysis. BJPsych Open / PMC. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12242034/
- National Institutes of Health, Office of Dietary Supplements. Ashwagandha: Health Professional Fact Sheet. Available at: https://ods.od.nih.gov/factsheets/Ashwagandha-HealthProfessional/