Introduction

Many people struggle with insomnia, restlessness, or a persistent sense of being wound up. While countless sleep aids and sedatives exist, more and more people are looking for natural alternatives with fewer side effects. One of the best-known herbs in this category is valerian root (Valeriana officinalis). This herb has been used since antiquity to support sleep, relaxation, and nervous system balance.

An important point to note up front: there is no health claim for valerian approved by the European Food Safety Authority (EFSA). The information below is intended for general education about what scientific research has shown so far, and not as medical advice or as a claim that valerian treats or prevents any specific condition.

Modern laboratory and animal research suggests that valerian may act on the central nervous system, primarily through the neurotransmitter system of GABA (gamma-aminobutyric acid). Some of this research has since been tested in small-scale human studies as well. Below, you can read how this mechanism of action is believed to work, what has and has not been demonstrated, and what the possible benefits and risks are.

1. What Is Valerian Root?

Valerian is a perennial plant with fragrant pink or white flowers. The root contains a complex mixture of bioactive compounds, including:

• Valerenic acid and valerenol

• Sesquiterpenes

• Valepotriates

• Isovaleric acid

These compounds are thought to affect the nervous system in several ways, primarily through interaction with GABA receptors. GABA is the primary inhibitory neurotransmitter in the brain: it helps reduce neural activity and promotes relaxation.

2. How Might Valerian Work on the Nervous System?

It is important to draw a clear distinction here between what has been demonstrated in laboratory research and animal studies, and what has been confirmed in humans.

What Laboratory and Animal Research Shows

In vitro enzyme assays and studies in rats show that valerian root extracts can slow the breakdown of GABA by inhibiting the enzyme GABA transaminase, and that they can stimulate GABA production by activating the enzyme glutamic acid decarboxylase. Cell culture and animal experiments have also shown that certain constituents, particularly valerenic acid and valerenol, can bind to specific subunits of the GABA-A receptor. One widely cited study in mice found that this receptor binding correlated with anxiety-reducing behavior in behavioral tests such as the elevated plus maze, and that this effect disappeared in mice with a genetic mutation in the relevant receptor subunit.

These findings are relevant because they suggest a plausible biological mechanism, but they come from cell culture and laboratory animals. That a substance inhibits an enzyme or binds to a receptor in a test tube or in a mouse does not automatically mean the same effect occurs to the same degree in humans.

What Has Been Studied in Humans

In humans, research has mainly examined end results, such as sleep quality and anxiety scores, rather than the underlying GABA mechanism itself. A systematic review and meta-analysis of 60 studies with nearly 6,900 participants in total concluded that valerian may improve subjective sleep quality and reduce anxiety, although outcomes varied considerably between studies, possibly due to differences in extract quality. Other, earlier meta-analyses were more cautious and described the evidence for objectively measurable effects as inconclusive.

GABA (gamma-aminobutyric acid) plays a central role in this proposed mechanism. It is the primary inhibitory neurotransmitter in the brain and functions as a kind of internal brake pedal that prevents the brain from continuing to race. Where activating substances such as glutamate essentially “switch on” the brain, GABA works to dampen signals and allow the brain to shift into rest. When GABA binds to its receptors, it slows electrical activity between neurons. This is essential for falling asleep, calming racing thoughts, and restoring emotional balance after stress.

If the GABA system is not functioning optimally, the brain may remain overly active. This can manifest as rumination, tension, anxiety, restlessness, or difficulty sleeping: the familiar feeling of being physically tired while the mind keeps spinning.

Based on the available laboratory and human data, it is thought that valerian aligns with this mechanism: the active compounds in the root may help ensure that more GABA remains available and that its effect becomes stronger. This could, in theory, reduce brain overactivity, slow racing thoughts, and help the body shift more easily into rest and sleep. This proposed mechanism may explain why valerian showed an effect on both insomnia and anxiety and stress in some studies, although further research in humans is still needed to confirm the precise mechanism of action.

3. Possible Benefits of Valerian

3.1 Support for Stress Management

There are indications that valerian may play a role in stress management. Animal research shows that the herb can increase GABA activity in the central nervous system, which theoretically contributes to less overstimulation. A small-scale human study using a single dose of valerian, administered before a stress task, showed a decrease in salivary cortisol levels and self-reported tension. However, this type of research is limited in scale and number, so caution is warranted before drawing general conclusions about cortisol and serotonin effects in humans.

These findings are nonetheless relevant, because chronic stress can disrupt a wide range of bodily functions. Prolonged tension can weaken the immune system, disturb sleep, affect mood, and raise blood pressure. Cognitive functions such as concentration, memory, and decision-making can also suffer. To the extent that valerian contributes to better sleep quality, this may indirectly support the body’s ability to recover from daily stressors as well.

3.2 Possible Support for Sleep

Of the applications of valerian that have been studied, this is the best supported in humans. The previously mentioned meta-analysis of 60 studies (n ≈ 6,894) found a statistically significant improvement in subjective sleep quality with repeated valerian use, particularly with use of the whole root or rhizome rather than isolated extracts. Objective sleep measures, such as polysomnography, showed less convincing results in some studies, suggesting that the effect appears to be most noticeable in how people perceive their own sleep.

The proposed mechanism is that valerian increases the availability of GABA in the brain, which may reduce overall brain activity. For many people, rumination, stress, and persistent tension keep the brain in a kind of alert state, even when the body is tired. By potentially acting on the GABA system, valerian may help the nervous system settle into rest.

3.3 Possible Effect on Blood Pressure

Research on valerian and blood pressure is limited in scope. A few small-scale human studies suggest a modest, statistically significant reduction in systolic and diastolic blood pressure in people with mild hypertension after several weeks of use, and a study in dental patients showed a dampened blood pressure and heart rate response to stress compared with placebo. These findings are promising, but the research base is still too small to draw firm conclusions. Larger and longer-term clinical trials are needed to confirm this effect.

To the extent that a relationship exists, it is thought to be related to valerian’s stress-reducing properties: when the body is in a state of alertness, adrenaline and cortisol levels rise, which increases heart rate and constricts blood vessels. A calming effect on the nervous system could, in theory, translate to the cardiovascular system, although this has not been sufficiently studied in humans specifically for valerian.

3.4 Possible Reduction in Anxiety and Inner Restlessness

Laboratory research in mice has shown that valerenic acid binds to a specific site on the GABA-A receptor, in a manner similar to how benzodiazepines such as diazepam (Valium) act on the same receptor system. This is a mechanistic similarity established in cell culture and in mice, not a directly proven equivalent effect in humans. That said, the previously mentioned meta-analysis in humans did find a statistically significant reduction in anxiety scores with valerian use across eight studies examined, which supports the idea that the herb may also have an anxiety-reducing effect in humans, albeit through a mechanism that is not yet fully understood.

Unlike benzodiazepines, valerian has not, to date, shown a demonstrated risk of physical dependence of the kind well documented with benzodiazepine use, although this remains a subject of ongoing research.

3.5 Possible Reduction in Menstrual Cramps

Of the applications discussed, this is one of the better supported in humans. Multiple randomized, placebo-controlled studies in women with primary dysmenorrhea (menstrual pain without an underlying condition) have found a reduction in pain intensity with valerian use around menstruation. A meta-analysis of five controlled trials with more than 400 participants in total calculated a significant pain reduction compared with placebo. In a comparative trial, valerian also performed no worse than the pain reliever mefenamic acid, with fewer reported side effects.

These findings are attributed to valerian’s antispasmodic (muscle-relaxing) properties. Menstrual pain arises because elevated prostaglandin levels cause the uterus to contract forcefully to shed the uterine lining. Valerian may dampen these contractions through a relaxing effect on smooth muscle tissue, although the exact mechanism in humans has not yet been fully established.

4. Risks and Side Effects

4.1 Possible Side Effects

Although valerian is generally considered safe, some people experience side effects such as headache, dizziness, or upset stomach. There are also reports of a paradoxical reaction, in which more tension or restlessness occurs instead of the expected calm. This individual variation is presumably related to differences in how each person’s GABA system responds to change, although this is not fully understood. It mainly underscores how individual the response to valerian can be, and why it is important to pay close attention to your own body’s signals when using it.

4.2 Interactions With Medications and Other Substances

Valerian may strengthen the effect of other substances that suppress the central nervous system, such as alcohol, benzodiazepines, opioids, sleep medications, certain antidepressants, and herbs such as St. John’s wort, kava, and melatonin. The underlying idea is that all of these substances reinforce inhibitory signals in the brain in some way, and that the effects can accumulate when combined, potentially resulting in excessive drowsiness or slowed reaction time.

It is important, however, to put this in perspective: a systematic review of interactions involving valerian preparations concluded that available in vitro and clinical studies could not demonstrate clinically relevant interactions via the major liver enzymes (CYP450), and that the interaction potential of valerian generally appears to be low. This does not eliminate the value of caution and consultation with a doctor or pharmacist when combining valerian with sedating substances, since the pharmacodynamic (functional) interaction via the GABA system can theoretically still occur even when there is no metabolic interaction via liver enzymes.

4.3 Not Suitable for Certain Groups

Valerian is not suitable for everyone. Use is not recommended for pregnant women or women who are breastfeeding, because insufficient research is available to confirm safety during these life stages. Caution is also warranted in children, since their nervous system responds differently and possibly more sensitively to substances that affect neurotransmitters.

In addition, caution is warranted in people with liver problems, since valerian is broken down in the liver. When liver function is reduced, the substance may accumulate in the body, which could lead to stronger or unpredictable effects. For all of these groups, medical advice is recommended before considering valerian.

4.4 Possible Withdrawal Symptoms With Long-Term Use

Withdrawal symptoms from valerian are rare, but not unknown. A published case report describes an older man with mild cognitive impairment who developed delirium after abruptly stopping long-term valerian use, with the researchers having ruled out other medical causes. The authors frame this in light of how other substances that act on the GABA-A receptor, such as barbiturates and benzodiazepines, can likewise cause delirium upon discontinuation because the inhibitory balance in the nervous system shifts suddenly.

This is an isolated case rather than broad epidemiological evidence, but it does illustrate that gradual tapering after long-term daily use is a sensible precaution, particularly for older adults or people with underlying vulnerabilities.

As a Final Note

As this article on valerian root shows, this is an herb with a long tradition and a growing, though not yet fully conclusive, scientific evidence base. For sleep support and menstrual pain, the human evidence is relatively strongest; for stress, blood pressure, and anxiety, the research is promising but still limited in scope. The underlying GABA mechanism is largely derived from laboratory and animal studies and should be interpreted with appropriate caution as an explanation for what happens in humans.

For most healthy adults, valerian appears to be safe at normal doses, but specific groups such as pregnant women, children, and people with liver problems are well advised to seek medical advice first. And as with most natural remedies, moderate, well-considered use is preferable to excessive use.

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