Benefits
Falling asleep and self-rated sleep quality
Results are inconsistent. In a review of 16 placebo-controlled trials, the 6 that reported a yes or no outcome favored valerian for better sleep, but the authors flagged weak methods and publication bias. A later review of 37 studies found that the most rigorous ones showed no difference from placebo, and a 2-week trial in older women with insomnia found no improvement in sleep onset or quality versus placebo.
Calm and relaxation
Valerenic acid enhances GABA-A receptor activity in cell and mouse studies, the proposed basis for a calming effect. Human evidence is thin: a pooled analysis of 8 single-herb studies (535 people) found large differences between studies and signs of missing negative results, a separate review found only one 36-person trial, and a 391-person online trial found no benefit over placebo.
Physical response to mental stress
In a laboratory study of 54 healthy volunteers, those who took valerian for 7 days had a smaller rise in systolic blood pressure and heart rate during a stressful mental task and reported feeling less pressure, while an untreated group did not change. There was no placebo group, so expectation effects cannot be ruled out.
Hot flash frequency and severity
Two small placebo-controlled trials in menopausal and postmenopausal women in Iran (68 and 60 women) reported milder hot flashes after about two months of valerian capsules. Both also reported fewer hot flashes, though one paper's frequency data appear to contain errors. These are two small trials from one country.
Mechanism of action
GABA-A receptor modulation
Valerenic acid and valerenol bind GABA-A receptors with high affinity and enhance responses to GABA in cell studies. In mice, valerenic acid lowered anxiety-like behavior, and this effect disappeared when a point mutation was introduced into the beta3 subunit. The EU herbal monograph reports no human pharmacokinetic data, so how much reaches the brain at supplement doses is unknown.
Adenosine A1 receptor activity
In cell membrane studies, valerian extracts and a valerian and hops combination bound selectively to adenosine A1 receptors and acted as partial activators. This has not been tested in people.
Clinical trials
Systematic review and meta-analysis of randomized, placebo-controlled trials of valerian for sleep; doses, preparations and treatment lengths varied widely, and most trials had significant methodological problems (Bent et al. 2006, Am J Med).
1,093 participants across 16 trials.
Six trials reported a yes or no sleep quality outcome; pooled, valerian users were about 1.8 times as likely as placebo users to report improved sleep (95% CI 1.2 to 2.9). The authors found evidence of publication bias.
Randomized, double-blind, placebo-controlled trial of valerian root capsules three times daily (255 mg in the abstract, 225 mg in the methods) versus starch placebo for 8 weeks at health centers in Zanjan, Iran (Mirabi et al. 2013, Iran J Pharm Res).
68 menopausal women with hot flashes.
Hot flash severity fell significantly more with valerian than with placebo (p<0.001). The paper also reports fewer hot flashes with valerian at 4 and 8 weeks, though parts of its frequency data appear to contain errors (implausible standard deviations, and timepoints in the methods that differ from the results). Recorded side effects did not differ between groups.
Triple-blind, randomized, placebo-controlled trial of a 530 mg valerian capsule twice daily versus a 530 mg starch placebo for two months, scored with the Kupperman index (Jenabi et al. 2018, Women Health).
60 postmenopausal women aged 45 to 55 in Hamadan, Iran.
Hot flash severity was significantly lower with valerian than with placebo at one month (p = .048) and two months (p = .020), and hot flash frequency was significantly lower at two months (p = .033).
NIH-supported phase 2 randomized, double-blind, placebo-controlled crossover trial of 300 mg concentrated valerian extract 30 minutes before bed for 2 weeks per period, measured by polysomnography, actigraphy, sleep logs and questionnaires (Taibi et al. 2009, Sleep Med).
16 older women with insomnia, mean age 69.
No significant difference from placebo in sleep latency, wake time after sleep onset, sleep efficiency or self-rated sleep quality. Wake time after sleep onset rose by about 18 minutes after valerian (p = .02) but not after placebo. Side effects were minor and similar between groups.
Randomized, double-blind, placebo-controlled trial run entirely over the internet, with kava, valerian and double placebo arms for 28 days; doses are not given in the abstract (Jacobs et al. 2005, Medicine (Baltimore)).
391 adults with elevated anxiety scores and insomnia; 135 were assigned to valerian and 135 to double placebo.
Neither valerian nor kava reduced anxiety or insomnia more than placebo. On the Insomnia Severity Index the placebo group improved by 8.3 points, and the valerian group improved 0.4 points less (95% CI from 1.3 points more to 2.1 points less).
Controlled laboratory study with kava, valerian and untreated control groups; responses to a mental task were measured before and after a week of a dose the abstract calls standard, with no placebo (Cropley et al. 2002, Phytother Res).
54 healthy volunteers, 18 per group.
After a week, the rise in systolic blood pressure during the task was smaller in the valerian and kava groups, heart rate reactivity fell only with valerian, and both groups reported feeling less pressure; the untreated group did not change. Diastolic blood pressure and task performance did not differ.