Valerian Root for Sleep: 60 Studies, and Why They Disagreed

Valerian is the herbal sleep aid that everyone has heard of, and it sits in a strange position: enormously popular, genuinely old, reliably safe, and unable to demonstrate that it works. Three documents cover the ground, and reading them together gives a more useful answer than any one of them alone.

What the sleep guideline says, in its own words

The American Academy of Sleep Medicine’s clinical practice guideline on the pharmacologic treatment of chronic insomnia lists individual agents and issues a recommendation for each. On valerian it says:

We suggest that clinicians not use valerian as a treatment for sleep onset or sleep maintenance insomnia (versus no treatment) in adults. (WEAK)

That is a recommendation against, at WEAK strength under the GRADE system. The guideline is careful about what WEAK means, and it is worth quoting because it cuts both ways: a weak recommendation “reflects a lower degree of certainty in the outcome and appropriateness of the patient-care strategy for all patients, but should not be construed as an indication of ineffectiveness.”

So this is not the guideline declaring that valerian does nothing. It is the guideline saying the evidence is not there to recommend it.

The comparison nobody makes: melatonin gets the same verdict

Search for valerian against melatonin and you will find a great many pages picking a winner. The guideline picks neither. Its melatonin recommendation is the same sentence with one word changed:

We suggest that clinicians not use melatonin as a treatment for sleep onset or sleep maintenance insomnia (versus no treatment) in adults. (WEAK)

Same direction, same strength. Diphenhydramine — the sedating antihistamine in most over-the-counter night-time products — and tryptophan and trazodone all receive recommendations against as well. The over-the-counter sleep aisle is, in guideline terms, largely a list of things the guideline suggests clinicians not use.

We go through the melatonin recommendation and its two honest qualifications in melatonin for insomnia: what the sleep guideline says.

The 2024 umbrella review: no evidence of efficacy

An umbrella review sits one level above a meta-analysis: instead of pooling trials, it pools systematic reviews. The 2024 example in European Neuropsychopharmacology screened 70 records and found 8 eligible reviews. Its conclusion has two halves and both matter:

• On efficacy: “the results showed no evidence of efficacy for the treatment of insomnia”
• On safety: valerian “has a good safety profile”

That is the sentence to carry away. Not dangerous. Not demonstrated.

The 2020 meta-analysis explains why the trials disagree

The most useful of the three papers is the one least often quoted accurately. A 2020 systematic review and meta-analysis covered 60 studies and 6,894 people, with meta-analyses on subjective sleep quality (10 studies, 1,065 people) and anxiety (8 studies, 535 people).

Its central observation is not about whether valerian works. It is about why nobody can tell:

inconsistent outcomes were possibly due to the variable quality of herbal extracts

and that

more reliable effects could be expected from the whole root/rhizome

The authors note that valerian contains multiple active constituents, that some are relatively unstable, and that quality control — standardisation methods and shelf life — may need revising. They reached a more optimistic overall conclusion than the umbrella review did, describing valerian as potentially “a safe and effective herb to promote sleep”.

Two serious reviews, published four years apart, reading the same literature and landing in different places. We are not going to pretend that is settled. What both agree on is the safety, and what the earlier one adds is the reason for the mess: two valerian trials are often not testing the same material.

Side effects, and what “safe” is actually based on

Across those 60 studies there were no severe adverse events, in subjects aged between 7 and 80 years. That is a reasonable evidence base for calling it well tolerated.

What gets reported in practice is mild: headache, stomach upset, next-morning grogginess in some people, and in a minority the opposite of the intended effect — feeling wired rather than sleepy. None of that is dangerous, but the paradoxical response is worth knowing about before you conclude that you personally have broken sleep beyond repair.

Two cautions are real:

• Do not stack sedatives. Valerian may add to alcohol, prescription sleeping medication and sedating antihistamines. That combination is where a benign herb stops being benign.
• Not in pregnancy or breastfeeding. There is no data, and no data is not the same as reassurance.

Dose: why the milligram number means less than you think

We are deliberately not printing a dose, and the reason is the finding above rather than caution for its own sake. A milligram figure is only meaningful alongside the extract it describes, and the reviews could not reconcile the trials precisely because the preparations were not equivalent. The same number on two different bottles is not the same dose, which is how sixty studies ended up disagreeing with each other.

If you are going to try it, the thing to read on the label is what the extract is made from and whether anyone has tested the batch — not the number on the front.

The smell is not a defect

Valerian root smells strongly and unpleasantly, usually described as old socks. The compound responsible is isovaleric acid, the same one behind the smell of stale sweat.

This is a feature of the material rather than a sign of a bad product. Valerian root that smells of nothing is generally old or weakly extracted. It is also why cats are interested in it: many respond to valerian much as they do to catnip, which is why it appears in cat toys. If the smell is what stops you persisting, that is a practical argument for capsules or drops over loose root and tea.

The honest bottom line

Valerian is safe, it is old, it is popular, and the best available synthesis of the evidence says nobody has shown it treats insomnia. The sleep guideline suggests clinicians not use it, and says the same about melatonin, diphenhydramine and tryptophan — so “the guideline is against it” is not the damning fact it sounds like in isolation, it is the ordinary state of the over-the-counter sleep aisle.

If your sleep problem is chronic, the treatment with actual guideline support is cognitive behavioural therapy for insomnia rather than anything in a bottle. If you want to try valerian anyway on a low-risk, self-experiment basis, that is a defensible thing to do — just control the one variable that sixty studies failed to control, and know what is in the bottle.