Valerian: Traditional Use, Constituents and Evidence

My nan kept a small clump of valerian at the back fence, wedged between the lemon balm and a sprawling rosemary that had clearly decided the fence was optional. She never called it by its Latin name. It was just "the smell one" , and she wasn't wrong. Cut the root and you'll understand immediately. That slightly sour, earthy funk has followed this plant through two millennia of recorded use, and I'd argue it's partly why researchers still argue about how it actually works: the chemistry is complicated, the smell puts people off standardising it properly, and the human trials have been frustratingly inconsistent.

But let's start at the beginning.

A plant with a very long paper trail

Valerian (Valeriana officinalis L., Caprifoliaceae) has been documented in European herbal medicine since at least the 1st century CE. Dioscorides listed it in De Materia Medica under the name phu , reportedly an exclamation about the smell. By the medieval period it was appearing across monastery herb gardens from the Rhine to the Danube, used in preparations associated with nervous restlessness and sleep. The 16th-century herbalist Leonhart Fuchs included it in his De Historia Stirpium (1542), and it remained a consistent presence in European and then British herbal tradition through to the 19th century.

In Australia, valerian arrived with European settlement and has been commercially sold here in various forms ever since. It now appears on the Australian Register of Therapeutic Goods (ARTG) , listed rather than registered; which means products containing it have been assessed for quality and safety by the TGA but have not undergone the full pre-market efficacy evaluation that registered medicines require. That distinction matters. A listed complementary medicine carrying an "AUST L" number can make only "low-level" health claims that are pre-approved by the TGA; it cannot claim to treat a diagnosed condition. You can read more about what ARTG listing means in our ARTG glossary entry.

Worth noting: valerian does not carry the import restrictions that apply to some other traditional-use botanicals in Australia. Kava, for example, faces specific personal-import controls under Schedule 10 of the Customs (Prohibited Imports) Regulations 1956. Valerian preparations have no equivalent restriction at time of writing, though all complementary medicines must still meet TGA manufacturing standards, including Good Manufacturing Practice (GMP) requirements for finished products.

Key constituents: a messy but interesting picture

The phytochemistry of valerian root is one of the reasons this plant attracts ongoing research. Several constituent classes have been identified, and the honest answer is that no single compound has been definitively shown to account for any observed biological activity in humans.

The main groups are:

• Valerenic acid and its derivatives, sesquiterpene acids, often used as marker compounds for standardised extracts. Valerenic acid has been studied in cell and animal models for its interactions with GABA-A receptor subunits.
• Isovaleric acid; largely responsible for the characteristic odour; a short-chain fatty acid produced partly by enzymatic degradation during drying and processing.
• Iridoids (valepotriates), bicyclic monoterpene compounds including valtrate, isovaltrate, and acevaltrate. These are chemically unstable; they degrade readily during drying, storage, and digestion, which complicates both standardisation and interpretation of older clinical studies.
• Flavonoids, including linarin and hesperidin, present in some species.
• Free amino acids; including gamma-aminobutyric acid (GABA) itself, though the extent to which orally ingested GABA crosses the blood-brain barrier in humans remains debated in the primary literature.
• Volatile compounds, including linalool, bornyl isovalerate, and other terpenoids that contribute to the aromatic profile. If you've spent any time reading about terpenes in plant medicine more broadly, you'll recognise this category as one where mechanistic speculation often runs well ahead of human evidence.

The instability of valepotriates is, honestly, a bit of a methodological headache. Many early trials used aqueous extracts or preparations in which these compounds would have already substantially degraded, meaning the "active fraction" being studied wasn't actually what researchers thought. More recent work tends to use defined hydroethanolic extracts standardised to valerenic acid content, but even then, the pharmacokinetics in humans are not fully characterised.

What the research actually shows, and where it stops

There is a reasonably substantial body of clinical trial literature on valerian, mostly focused on sleep outcomes. A 2006 systematic review published in the American Journal of Medicine (Bent et al.) identified 16 randomised, double-blind trials. The authors concluded that valerian "may improve sleep quality without producing side effects," but noted the evidence was not sufficient to draw firm conclusions. That's a measured finding; and a decade and a half later, the picture hasn't changed as dramatically as you might hope.

A 2020 systematic review and meta-analysis by Shinjyo, Waddell, and Green in Journal of Evidence-Based Integrative Medicine looked at a broader set of studies and reported heterogeneous results, with some trials showing statistically significant effects on subjective sleep quality and others showing no difference from placebo. The authors identified methodological limitations across the literature: small sample sizes, poorly validated outcome measures, variable extract compositions, and short study durations. These are not minor caveats. They're the kind of limitations that prevent any confident efficacy claim from being made, and the TGA's listed-medicine framework reflects exactly that position.

It's worth being precise: nothing in this body of research permits a claim that valerian treats insomnia, anxiety disorders, or any other diagnosed condition. Describing mechanisms under investigation is different from asserting clinical effect, and I'd be doing this plant a disservice by conflating the two.

GABA receptor interactions and mechanistic hypotheses

The most frequently discussed proposed mechanism involves the GABAergic system. Valerenic acid has been shown in in vitro and animal studies to modulate GABA-A receptor activity, specifically, some research suggests it may act as a positive allosteric modulator at certain receptor subunits, somewhat analogously (though not identically) to how benzodiazepines work. This is a genuinely interesting area of phytomedicine research.

The reason I mention the endocannabinoid system here isn't to imply valerian is a cannabinoid; it isn't. But understanding how botanicals interact with receptor systems more broadly is part of the same field. Several terpene compounds found in valerian, including linalool, also appear in cannabis and other aromatic plants, and some researchers have explored whether they might interact with multiple receptor families. The evidence for any such interaction in valerian specifically is preliminary and should be read as mechanistic hypothesis rather than established pharmacology.

The first-pass metabolism question also applies here: how much of any orally consumed constituent actually reaches systemic circulation in a form relevant to central nervous system activity? For most of the valerian constituents studied to date, the answer is "we don't fully know." That's not a failure of the plant; it's a gap in the science.

Valerian as a phytomedicine, the regulatory and quality picture in Australia

The concept of a phytomedicine carries specific meaning: a medicinal product derived from plant material, standardised and manufactured to defined quality criteria, distinct from a crude folk preparation. Whether a given valerian product on an Australian shelf actually meets that standard varies considerably.

Products carrying an AUST L number have passed a TGA quality assessment and are manufactured under GMP. Products without such listing, grey-market imports, unregistered products sold through non-compliant channels; have no such assurance. Extract composition, valerenic acid content, absence of contaminants: none of these are guaranteed outside the regulated pathway. This is a practical consideration for anyone reading the research, because the extract used in a particular clinical trial may bear little resemblance to what's commercially available.

The TGA's guidance on complementary medicine evidence levels is publicly available at tga.gov.au, and I'd recommend it as a reference for anyone wanting to understand what "listed" versus "registered" actually means in the Australian context.

Where valerian sits in the broader botanical picture

Valerian is, for me, one of those plants that rewards patience. The history is genuinely rich, you can trace a line from Dioscorides through the Benedictine herb gardens all the way to a current-day Adelaide Hills nursery (I spotted it last spring at Carrick Hill's heritage garden in Springfield, tucked in beside the old lavender bed, which pleased me more than it probably should have).

The science is more complicated than the history. Two millennia of documented use doesn't constitute clinical evidence, but it does constitute a research lead worth taking seriously. The phytochemistry is genuinely intricate, the constituent interactions are still being worked out, and the clinical literature has real limitations that any honest reading has to acknowledge.

What we can say with confidence: valerian root contains a complex mixture of biologically active compounds, several of which have shown interesting activity in preclinical models. What remains unresolved is whether oral administration in humans produces clinically meaningful effects at typical doses, and which constituents might be responsible if it does. That's not a discouraging finding. It's just where the evidence actually sits.

Sources

• Listed medicines, evidence requirements; Therapeutic Goods Administration (TGA)
• Shinjyo N, Waddell G, Green J. Valerian Root in Treating Sleep Problems and Associated Disorders, A Systematic Review and Meta-Analysis. J Evid Based Integr Med. 2020, NCBI/PMC
• Bent S et al. Valerian for Sleep: A Systematic Review and Meta-Analysis. Am J Med. 2006; NCBI PubMed
• WHO Definitions: Traditional Medicine, World Health Organization

, Naomi Ellison, Botanical & phytomedicine writer

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