Research review
Does valerian root calm the nervous system or lower cortisol? What the research does and doesn't show
The one placebo-controlled human trial that measured cortisol used a four-herb combination that included valerian, not valerian alone, and found no difference from placebo in that biological stress marker, even though it reduced self-reported anxiety.
The evidence doesn't support valerian root, taken alone, as a proven way to calm the nervous system or lower cortisol. The one placebo-controlled human trial to measure cortisol tested a four-herb combination that included valerian, not valerian by itself, and found no difference from placebo.
What the evidence doesn't support
It doesn't support valerian root, alone, as a way to lower cortisol, calm the nervous system as a measured physiological outcome, or relax muscles. It doesn't support using valerian as a substitute for stress-management approaches that have been shown to work. The mechanism sometimes cited for its calming reputation is laboratory-level evidence, not a demonstrated human effect.
What the trials found
Valerian's proposed calming mechanism comes from laboratory research: valerenic acid, one of its compounds, has been shown in lab studies to slow the breakdown of GABA, a calming brain chemical. That's a plausible biochemical pathway identified in a test tube, not proof that a capsule or cup of tea measurably calms a person's nervous system (PMID 10411208).
A randomized, placebo-controlled trial tested a fixed combination of valerian, passionflower, lemon balm, and butterbur extracts — not valerian alone — in 72 healthy men exposed to a standardized psychosocial stress test. The combination didn't significantly change salivary cortisol, the biological stress marker, compared with placebo or no treatment, but it did significantly reduce self-reported anxiety versus both. Because four herbs were combined, the result can't be attributed to valerian specifically, and the trial's own conclusion was that the combination affected subjective stress perception without changing the biological stress response it measured (PMID 29433687).
A broader analysis of 8 trials (535 people) on situational anxiety — including the kind of stress from a medical or dental procedure, not only diagnosed anxiety disorders — found high statistical heterogeneity between trials (I²=93%) and evidence of publication bias. Results were more consistent in the two trials using whole root than in the trials using extract, which the reviewers themselves called too little data for a conclusion (PMID 33086877).
One placebo-controlled trial did find a physiological difference under acute stress: a single 100 mg dose of valerian, given to 20 healthy volunteers before dental surgery, was associated with steadier systolic blood pressure and heart rate afterward than placebo (PMID 24741279). That's a small trial, a single low dose, and a specific surgical-stress setting — not a general "calms the nervous system" finding that extends beyond it.
No trial identified for this page tested valerian root — Valeriana officinalis, the species used in commercial products — for muscle relaxation in people. Antispasmodic effects have been described in lab and animal research on a related but different species, Valeriana wallichii, which isn't the plant most commercial valerian root products use; that data doesn't transfer directly.
Questions people ask
Does valerian root calm the nervous system?
The proposed mechanism is a laboratory finding about how one of its compounds interacts with GABA. No trial reviewed here measured a "calmed nervous system" as a physiological outcome in people taking valerian alone.
Does valerian root lower cortisol?
The one placebo-controlled trial to measure cortisol found no significant difference from placebo — but it tested a four-herb combination, not valerian alone, so this doesn't rule out an effect from valerian by itself; it simply hasn't been tested.
Is valerian root good for relaxation?
The research is inconsistent: high heterogeneity and publication bias in the pooled situational-anxiety trials, alongside one small trial showing steadier vital signs under acute dental stress at a low dose. See valerian root benefits: what the research does and doesn't show for the fuller picture.
Does valerian root calm dogs?
This page and its citations cover valerian as a human supplement, studied in human trials. None of the research here applies to dogs — ask a veterinarian for animal-specific guidance.
Is valerian root good for muscle relaxation?
No human trial identified for this page tested valerian root for muscle relaxation. Related research on a different Valeriana species doesn't establish an effect for the species used in commercial valerian root products.
When to talk to a doctor
Ongoing stress that interferes with daily life is worth raising with a doctor or therapist. Valerian root is not a treatment for stress or an anxiety condition, and nothing in the research above supports using it as a substitute for approaches shown to work. If you take a prescription medication, especially anything sedating, or are pregnant or nursing, talk to a doctor before adding valerian.
Related reading: does valerian root help with anxiety?, valerian root benefits: what the research does and doesn't show, and valerian root side effects.
Sources
- The scientific basis for the reputed activity of Valerian A pharmacology review describes laboratory evidence that valerenic acid, one of valerian's compounds, slows the breakdown of GABA, a proposed mechanism for its traditional sedative reputation — laboratory-level evidence, not proof of effect in people.
- Effects of a fixed herbal drug combination (Ze 185) to an experimental acute stress setting in healthy men - An explorative randomized placebo-controlled double-blind study A placebo-controlled trial of a four-herb combination that included valerian (not valerian alone) found no significant difference in cortisol between groups, while self-reported anxiety during an acute stress test was lower with the combination than with placebo.
- Valerian Root in Treating Sleep Problems and Associated Disorders-A Systematic Review and Meta-Analysis A 2020 systematic review of 60 studies found a small, not-statistically-significant pooled effect of valerian on sleep quality overall, a higher (but still uncertain) effect for whole root versus extract, and high heterogeneity in its anxiety meta-analysis; individual trial results ranged from no effect to modest subjective improvement.
- Valeriana officinalis L. for conscious sedation of patients submitted to impacted lower third molar surgery: A randomized, double-blind, placebo-controlled split-mouth study A small placebo-controlled trial found a single 100 mg dose of valerian, given before dental surgery, was linked to steadier systolic blood pressure and heart rate afterward than placebo, in 20 healthy young volunteers.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.