Reading the evidence
Tea or extract? Why most calming-tea studies didn't test tea
Published · By Calm Teas (how we work)
Key takeaways
- An extract concentrates a herb into a measured dose; a tea is a few grams of dried plant steeped in hot water. Results don't transfer automatically.
- In our index, only chamomile, lavender and passionflower have controlled human trials given as tea for sleep, anxiety or mood, and most of those had no placebo drink.
- Ask three questions of any study: what form, compared with what, and in whom?
Why does the form matter?
An extract is made by concentrating a plant’s compounds, often with alcohol or other solvents, into a measured dose. A tea is dried plant steeped in hot water; the EU herbal monographs describe traditional amounts of roughly 0.3 to 4.5 g per cup, depending on the herb. They differ in how much of the herb you get and which compounds come through.
Take lemon balm. A lab study that found more calm used a single 600 mg dose of a standardized extract (Kennedy et al., 2004). The EU herbal monograph describes the traditional tea as 1.5–4.5 g of dried leaf in 150 ml of water, without claiming the two are equivalent (EU herbal monograph). Ashwagandha sleep benefits were larger at 600 mg a day or more of extract for at least eight weeks (Cheah et al., 2021). L-theanine trials used isolated supplements (Bulman et al., 2025). A lavender anxiety result came from an oil capsule (Zhang et al., 2022).
None of that tells you what a tea bag will do.
Which calming herbs have actually been tested as tea?
| Herb | Evidence | Traditional tea amount (EU) | Teas in index |
|---|---|---|---|
| Chamomile | Tested as tea | 1.5–4 g per 150 ml | 29 |
| Lemon balm | Extract trials only | 1.5–4.5 g per 150 ml | 7 |
| Lavender | Tested as tea | 1–2 g per 150 ml | 10 |
| Passionflower | Tested as tea | 1–2 g per 150 ml | 10 |
| Valerian root | Mixed results | 0.3–3 g per 150 ml | 4 |
| Linden flower | Traditional use only | 1.5 g per 150 ml | 7 |
| Hops | Extract trials only | 0.5–1 g per 150–200 ml | 2 |
| L-theanine (green tea) | Extract trials only | none listed | 0 |
| Ashwagandha | Extract trials only | none listed | 2 |
| Licorice root | Caution ingredient | none listed | 8 |
| St John's wort | Caution ingredient | none listed | 1 |
| Kava | Caution ingredient | none listed | 0 |
Even the “tested as tea” group is thin:
- Passionflower: one placebo-tea trial with 41 healthy young adults, one better sleep-quality rating (Ngan & Conduit, 2011).
- Chamomile: one trial against usual care (no placebo drink) (Chang & Chen, 2016); one placebo-tea trial of a blend that found no anxiety difference (Zampieri et al., 2025).
- Lavender: small trials compared with no drink at all (Bazrafshan et al., 2020).
How can I check a claim myself?
Ask three questions of any study a tea page cites:
- What form? Tea, extract, oil, capsule or isolated compound? If the abstract says “extract” or gives a milligram dose, it probably wasn’t tea.
- Compared with what? A placebo drink, nothing at all, or another treatment? Without a placebo, expectation and ritual can explain much of the effect.
- In whom, for how long? Healthy students for a week, or people with diagnosed insomnia for two months?
Why we bother
We grade each herb by the form that was tested. It makes the honest answer smaller, but it’s the one that applies to the cup in your hand. The full rubric is in our editorial policy.
Sources
- Ngan & Conduit (2011). A double-blind, placebo-controlled investigation of the effects of Passiflora incarnata (passionflower) herbal tea on subjective sleep quality. Phytother Res.
Human trial (randomized, double-blind, placebo tea, crossover) · form: tea
41 healthy adults aged 18–35 drank one cup of passionflower tea or a placebo tea nightly for a week each. Diary-rated sleep quality was better with passionflower; the other five diary measures were not reported as different.
Limits: Healthy young adults with mild sleep fluctuations; one week per arm; subjective outcome.
checked against the abstract, 2026-10-21 · PMID 21294203 - Zampieri et al. (2025). Exploring the Effects of a Calming Herbal Tea Blend on Perioperative Anxiety: A Randomized Clinical Trial. J Med Food.
Human trial (randomized, double-blind, placebo tea) · form: tea
210 surgical patients in Brazil drank a chamomile–passionflower–anise tea or a lemon placebo tea. Anxiety scores did not differ between groups; the herbal-tea group reported more positive feelings about the procedure.
Limits: Single centre; anxiety measured after surgery. A rare trial with a placebo tea, and it found no anxiety difference.
checked against the abstract, 2026-10-21 · PMID 39514279 - Chang & Chen (2016). Effects of an intervention with drinking chamomile tea on sleep quality and depression in sleep disturbed postnatal women: a randomized controlled trial. J Adv Nurs.
Human trial (randomized, no placebo) · form: tea
80 postnatal women in Taiwan with poor sleep drank chamomile tea for 2 weeks or received usual care. The tea group had lower scores for physical-symptom-related sleep inefficiency and depression at 2 weeks; the difference was gone at 4 weeks.
Limits: Control group got no placebo drink, so expectation effects can't be separated out. Short follow-up. One specific population.
checked against the abstract, 2026-10-21 · PMID 26483209 - Bazrafshan et al. (2020). The effect of lavender herbal tea on the anxiety and depression of the elderly: A randomized clinical trial. Complement Ther Med.
Human trial (randomized, single-blind, no placebo) · form: tea
60 older adults in Iran drank a 2 g lavender tea bag twice daily for 2 weeks or had no intervention. The tea group ended with lower depression and anxiety scores.
Limits: No placebo drink; single-blind; small; two weeks.
checked against the abstract, 2026-10-21 · PMID 32444033 - Kennedy et al. (2004). Attenuation of laboratory-induced stress in humans after acute administration of Melissa officinalis (Lemon Balm). Psychosom Med.
Human trial (randomized, double-blind crossover) · form: extract
18 healthy volunteers took single doses of a standardized lemon balm extract (300 mg, 600 mg) or placebo before a lab stress test. The 600 mg dose increased self-rated calmness.
Limits: Very small; single doses of an extract, not tea; healthy volunteers in a lab setting.
checked against the abstract, 2026-10-21 · PMID 15272110 - Cheah et al. (2021). Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLoS One.
Systematic review + meta-analysis · form: extract
5 randomized trials (400 adults). Ashwagandha extract had a small effect on overall sleep; larger in people with insomnia, at ≥600 mg/day and ≥8 weeks.
Limits: Extract doses; serious-adverse-event data limited.
checked against the abstract, 2026-10-21 · PMID 34559859 - Zhang et al. (2022). Medicinal herbs for the treatment of anxiety: A systematic review and network meta-analysis. Pharmacol Res.
Systematic review + network meta-analysis · form: extract
29 trials comparing 12 herbs for anxiety. A lavender-oil capsule (Silexan) and kava showed significant effects on anxiety scores; kava was possibly ineffective in generalized anxiety disorder.
Limits: Capsules and extracts, not teas; several herbs had few, small trials.
checked against the abstract, 2026-10-21 · PMID 35378276 - Bulman et al. (2025). The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis. Sleep Med Rev.
Systematic review + meta-analysis · form: supplement
19 articles (897 participants) on L-theanine supplements. Small improvements in subjective time to fall asleep, daytime dysfunction and overall sleep-quality scores.
Limits: Supplement doses, not tea; authors note few studies of pure L-theanine.
checked against the abstract, 2026-10-21 · PMID 40056718 - European Medicines Agency, HMPC. Community herbal monograph on Melissa officinalis L., folium (EMA/HMPC/196745/2012).
Regulatory monograph
Traditional use for mild symptoms of mental stress and to aid sleep, and mild digestive complaints. Tea: 1.5–4.5 g in 150 ml boiling water, 1–3 times daily; over 12 years. Pregnancy and lactation use not recommended for lack of data.
checked against the official document, 2026-10-21 - European Medicines Agency, HMPC. Community herbal monograph on Passiflora incarnata L., herba (EMA/HMPC/669740/2013).
Regulatory monograph
Traditional use for mild symptoms of mental stress and to aid sleep. Tea: 1–2 g in 150 ml boiling water, 1–4 times daily; adolescents and adults. Not recommended under 12 or in pregnancy/lactation for lack of data.
checked against the official document, 2026-10-21
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