Sleep herbs explained: valerian, passionflower, chamomile and lavender

Valerian, passionflower, chamomile, lavender: four herbs that turn up together on bedtime shelves, tea boxes and capsule blends as if they were one cosy committee. They aren't. They come from different plants, have been tested in different ways, and carry different cautions. Let's take them one at a time, then see why a label that lists all four tells you less than it seems to.

Four herbs, four different evidence stories

Each of these herbs has a long history as a bedtime plant, and each has some human research behind it, but none has a settled, strong evidence base for treating sleep problems. In rough order of what the research turned up:

• Valerian has the most trials and several systematic reviews, with mixed conclusions: some improvement in how people rate their sleep, little consistent change in measured sleep.
• Passionflower has a handful of small trials, including one polysomnography study in 110 adults with insomnia disorder that found a modest increase in total sleep time.
• Chamomile has small trials and recent meta-analyses pointing to better questionnaire scores, with high variation between studies and one insomnia-specific trial that found no significant difference.
• Lavender is a different case. The best-studied form is a specific oral lavender oil (Silexan) tested in people with anxiety, where sleep improved mainly alongside anxiety. Inhaled lavender is a separate, weaker-quality body of research.

They are not interchangeable, and the differences matter for safety as well as evidence. Most of the trials are short (days to ten weeks), small, and rely on self-reported sleep.

Why the evidence is hard to read

Herbal trials vary in ways drug trials usually don't. The plant part, extract method, standardisation and dose differ between studies, so "valerian" in one trial is not the same product as "valerian" in the next. Many studies run for a week or two and rely on questionnaires. Blinding is tricky when the product has a strong smell or taste. And a statistically significant change in a score isn't automatically a change you'd notice.

Two other things to keep in mind throughout:

• Traditional use isn't a trial. The EU's Committee on Herbal Medicinal Products (HMPC) can support a "traditional use" indication based on decades of documented use, which is a different test from clinical efficacy. EMA's public pages describe valerian root's traditional use in these terms.
• Official US guidance is cautious. NCCIH's sleep disorders overview (updated May 2024) says valerian trials have had inconsistent results and its value for insomnia hasn't been demonstrated, and that for chamomile there's no conclusive clinical evidence of help.

Valerian

What it is

Valerian supplements come from the root (and rhizome) of Valeriana officinalis. It's a traditional European plant, and the EMA's public summary lists its traditional use as "relief of mild symptoms of mental stress and to aid to sleep" (EMA page updated 11 March 2026; monograph adopted 2016).

What the trials say

Four reviews, three different verdicts, and the gap is partly down to which trials each one counted. Bent et al., 2006 pooled 16 randomised, placebo-controlled studies (1,093 patients) in the American Journal of Medicine. Six reported a yes/no improvement in sleep quality, which favoured valerian (relative risk 1.8), but the authors saw evidence of publication bias, said most studies had significant methodological problems, and noted that doses, preparations and treatment length varied widely.

A year later, Taibi et al., 2007 in Sleep Medicine Reviews looked at 29 controlled trials and came out cooler: most showed no significant difference between valerian and placebo, and none of the most recent, most rigorous studies found significant effects. Their conclusion was that valerian is safe but the evidence doesn't support efficacy for insomnia.

The middle ground came from Fernández-San-Martín et al., 2010 in Sleep Medicine, a meta-analysis of 18 trials. It found a relative risk of 1.37 for self-reported improvement, but no difference from placebo in time to fall asleep (0.7 minutes) or in a sleep-quality scale, so valerian might help subjective insomnia without being shown on quantitative or objective measures. The most upbeat is Shinjyo et al., 2020 in the Journal of Evidence-Based Integrative Medicine: 60 studies (6,894 participants), with meta-analyses of subjective sleep quality (10 studies) and anxiety (8 studies). It concluded valerian could be a safe and effective herb for sleep, and suggested inconsistent results may reflect extract quality, with whole root perhaps working more reliably than some extracts. That last point is the authors' interpretation, not a tested finding.

In short: the reviews disagree because they include different trials and ask different questions. A fair reading is that some people report better sleep on valerian in some studies, the effect on measured sleep is not clearly shown, and product quality varies.

Safety

• NCCIH's valerian page (updated May 2025) says the evidence for sleep is inconsistent, and the American Academy of Sleep Medicine advises against valerian for chronic insomnia in adults. It lists possible side effects including headache, stomach upset, mental dullness, excitability, uneasiness and vivid dreams, and says abrupt discontinuation after long-term use can cause withdrawal symptoms such as anxiety and insomnia.
• The same page describes rare cases of liver injury, usually involving other herbal products too, with long-term liver effects unknown. Individual case reports exist in the literature (for example Cohen and Del Toro, 2008).
• NCCIH says valerian shouldn't be combined with alcohol or sedatives because of possible additive effects.
• EMA's public summary says not to use valerian root medicines in pregnancy or when breastfeeding, not in children under 12, and not to drive or operate machinery. It lists nausea and abdominal cramps as undesirable effects of unknown frequency, and says no medicine interactions had been described at the time of assessment.

Passionflower

What it is

Passiflora incarnata is a climbing vine whose above-ground parts are used in teas and extracts. There are hundreds of Passiflora species, and the trials we found name P. incarnata, so it's worth checking a label's species. EMA lists traditional use of passion flower herb for "relief of mild symptoms of mental stress and to aid sleep" in adults and adolescents over 12 (monograph revised 2014).

What the trials say

The small end first. Ngan and Conduit, 2011 (Phytotherapy Research) ran a double-blind, placebo-controlled crossover study in which 41 healthy adults aged 18 to 35 drank a cup of passionflower tea or placebo tea for a week each. Of six sleep-diary measures, only sleep quality was rated significantly better with passionflower. A subgroup of ten had polysomnography. The authors describe a short-term subjective benefit in people with mild fluctuations in sleep quality.

The more interesting trial is Lee et al., 2020 (International Clinical Psychopharmacology): a double-blind, placebo-controlled study of 110 adults with insomnia disorder. Total sleep time on polysomnography increased more with a passionflower extract than with placebo over two weeks (about 23 minutes versus roughly no change, p = 0.049, so only just). Sleep efficiency and time awake after sleep onset improved within the passionflower group but did not differ significantly from placebo, and the authors say more study is needed.

One more study gets quoted a lot, and it isn't about sleep. A Cochrane review of passiflora for anxiety found two eligible studies (198 participants) and concluded trials were too few to draw conclusions; one study showed no difference in efficacy from a benzodiazepine. That's sometimes retold as "passionflower works as well as a prescription drug", which overstates what two small anxiety studies can show.

NCCIH's passionflower page (updated April 2025) summarises the picture as oral passionflower possibly improving total sleep time in adults with insomnia, with mixed effects on time to fall asleep and stay asleep.

Safety

The same NCCIH page says passionflower appears reasonably safe in the short term (tea for up to seven nights, extract daily for up to eight weeks in the studies it cites), that it should be avoided in pregnancy because it may induce uterine contractions, and that drowsiness, dizziness and confusion are possible side effects. It also advises stopping it at least two weeks before scheduled surgery because it may interact with anaesthesia. EMA's summary advises consulting a healthcare practitioner if symptoms persist beyond two weeks.

Chamomile

What it is

The chamomile in tea bags and capsules is usually Matricaria chamomilla (also called Matricaria recutita, German chamomile). One interesting detail: EMA's herbal monograph pages for chamomile flower list uses such as minor digestive complaints, colds, and mouth, throat and skin problems. Sleep isn't among them. Chamomile's reputation as a sleep herb is traditional and popular rather than part of that official indication.

What the trials say

The insomnia-specific trials are small and not very encouraging. Zick et al., 2011 (BMC Complementary and Alternative Medicine) randomised 34 adults with chronic primary insomnia to 270 mg of a chamomile extract twice daily or placebo for 28 days. Sleep-diary measures showed no significant differences, with a modest, non-significant edge for chamomile on daytime functioning.

The more positive results come from other groups. Chang and Chen, 2016 (Journal of Advanced Nursing) studied 80 postnatal women with poor sleep: two weeks of chamomile tea was associated with lower scores for sleep inefficiency (physical symptoms) and depressive symptoms than regular care alone, but scores were similar between groups at four weeks, and the control group had no placebo tea. Adib-Hajbaghery and Mousavi, 2017 (Complementary Therapies in Medicine) gave 200 mg chamomile extract capsules twice daily for 28 days to 60 people aged 60 or over in an Iranian nursing-home day-care setting, against wheat-flour capsules, in a single-blind trial. Sleep quality on the Pittsburgh Sleep Quality Index was significantly better with chamomile.

The reviews smooth these into a general lean towards better questionnaire scores, with plenty of caveats. A 2019 systematic review and meta-analysis in Phytotherapy Research (12 randomised trials) found improved sleep quality scores overall (standardised mean difference -0.73), but only one trial was on insomnia, and it found no significant change. A 2024 review in Complementary Therapies in Medicine (10 studies, 772 participants) found a lower Pittsburgh Sleep Quality Index score (by 1.88 points on average, with very high heterogeneity, I² 88%) and improvement in awakenings in some studies, but no change in sleep duration or efficiency. It also noted that only one study checked whether blinding worked and tested product purity or potency.

NCCIH's chamomile page (updated November 2024) notes one insomnia study in a 2019 review that found no benefit, and says preliminary research suggests chamomile might help generalised anxiety disorder.

Safety

NCCIH says side effects are uncommon but include nausea, dizziness and allergic reactions, including severe hypersensitivity and anaphylaxis in some people. People allergic to ragweed, chrysanthemums, marigolds or daisies are at higher risk. EMA's chamomile flower summary says the medicine must not be used by people allergic to chamomile flowers or other Asteraceae (daisy family) plants. NCCIH also says interactions with some liver-metabolised drugs and with warfarin have been reported, and that little is known about safety in pregnancy or breastfeeding.

Lavender

What it is

Lavender in sleep products is Lavandula angustifolia, used in two quite different ways: as an oral capsule of lavender oil, and as an inhaled essential oil or aromatherapy product. They shouldn't be lumped together. EMA lists a lavender flower monograph (adopted 2012) in the therapeutic areas of sleep disorders and temporary insomnia.

Oral lavender oil (Silexan)

Silexan is a specific, patented lavender oil preparation sold as capsules. Much of the sleep-related evidence comes from trials in people with anxiety, not insomnia.

Two studies, one story. Kasper et al., 2015 (European Neuropsychopharmacology) was a randomised, placebo-controlled trial of 170 outpatients with anxiety-related restlessness and disturbed sleep, given 80 mg Silexan or placebo daily for ten weeks. Anxiety scores fell more with Silexan (group difference p = 0.03), and the authors report a larger treatment effect than placebo on all outcome measures, including the Pittsburgh Sleep Quality Index. Adverse events were reported by 33.7% on Silexan and 35.7% on placebo.

Then Seifritz et al., 2019 (Journal of Psychiatric Research) ran a mediation analysis of 212 patients and found Silexan improved sleep scores, with 98.4% of that effect explained by reduced anxiety and a negligible direct effect on sleep. A 2022 narrative review by the same group reached the same conclusion. Much of this research comes from authors linked to the Silexan research programme, and we haven't looked at who funded it.

What that means: in these studies Silexan helped sleep as anxiety improved. That's relevant if anxiety is what keeps you awake, and it isn't evidence that lavender capsules work as a sleep aid in people whose sleep problem isn't anxiety-driven. Other lavender oil capsules aren't necessarily the same preparation.

Inhaled lavender

A 2026 systematic review and meta-analysis in Holistic Nursing Practice of 11 randomised trials (628 adults) reported that inhaled lavender essential oil improved sleep quality (standardised mean difference -0.56), while the authors caution that the number and quality of the included studies limits confidence. A 2018 JBI review found no studies directly comparing oral Silexan with inhaled lavender, so one shouldn't be taken as evidence for the other. NCCIH's lavender page (updated February 2025) says it's unclear whether lavender aromatherapy helps sleep quality or insomnia, and that an oral lavender oil product might help anxiety.

Safety

NCCIH lists diarrhoea, headache, nausea or burping as common reactions to oral lavender, and headache or coughing from aromatherapy. It also notes a few reports of breast tissue swelling in children using topical products containing lavender, with unclear causation. We did not find a source clearing oral lavender oil for use in pregnancy.

Side by side

• : Plant part used; Valerian: Root and rhizome; Passionflower: Above-ground parts; Chamomile: Flower; Lavender: Flower (oil or flowers)
• : Best-supported use; Valerian: Self-rated sleep quality (mixed); Passionflower: Subjective sleep quality; one trial with a small gain in total sleep time; Chamomile: Questionnaire sleep quality in small trials; Lavender: Anxiety-related restlessness and disturbed sleep (oral oil)
• : Where evidence is weakest; Valerian: Objective sleep measures; Passionflower: Few trials, short durations; Chamomile: Insomnia-specific trial found no difference; Lavender: Inhaled form: low-quality studies; oral form: anxiety populations
• : Notable cautions in sources; Valerian: Liver reports (rare), sedatives and alcohol, pregnancy and breastfeeding, under-12s; Passionflower: Pregnancy, surgery and anaesthesia; Chamomile: Daisy-family allergy, warfarin; Lavender: Digestive effects, topical use in children
• : EMA traditional-use sleep wording; Valerian: Yes; Passionflower: Yes; Chamomile: No (sleep isn't among the listed uses); Lavender: Monograph lists sleep disorders (summary page only)

Reading a four-herb label

A label reading "valerian, passionflower, chamomile, lavender" tells you which herbs are present, but it doesn't tell you:

• Which plant part and preparation. Tea, tincture, dry extract and essential oil are different products.
• How much of each. Many blends use "proprietary blend" totals.
• Whether the studied form matches. The evidence above is for specific preparations: valerian root extracts of varying types, Passiflora incarnata tea or extract, chamomile tea or extract, and Silexan.
• What the blend as a whole has been tested for. We did not find reviewed trials of specific four-herb blends, so the evidence for any one of them can't be assumed to apply to the combination.

Treat any blend like a stack: every ingredient adds its own cautions, and the safety notes above apply cumulatively. If you take medicines, especially sedatives, anticoagulants such as warfarin, or have a known daisy-family allergy, check before buying. Our guide to supplement and drug interactions explains how, and our label-reading guide covers the basics.

A warm cup, a modest evidence base

These herbs are interesting, and plenty of people find a warm cup of something calming a pleasant part of winding down. The research doesn't show that any of them reliably fixes sleep problems, and the best-supported claims are narrow: passionflower and valerian for self-rated sleep in some studies, chamomile for questionnaire scores, lavender oil for anxiety-linked sleep disturbance. If sleep trouble lasts more than a few weeks, see a doctor. Our sleep hygiene guide covers the habits that research supports more strongly than any single herb.

Where to read next

From the smartshop shelf:

• Dream herbs explained: African dream root, seed and uvuma-omhlophe, for which plants the labels name, what the sources describe and where the research stops.

Written by Smart Supplements with AI assistance from the sources linked in the text. It has not been reviewed by a clinician.

Last updated: 12 October 2026

This article is for informational purposes only and is not intended as medical advice. Always consult a healthcare professional before starting any new supplement, especially if you take prescription medication.