What Herbs Calm the Nervous System?

A surprisingly large number of herbs have measurable calming effects on the nervous system, and the evidence behind them is more specific than most people expect. Valerian, passionflower, chamomile, lemon balm, lavender, ashwagandha, holy basil, kava, and skullcap all have preclinical and clinical data supporting their anxiolytic or sedative properties. A 2018 systematic review identified ten phytomedicines with both laboratory evidence of interaction with the brain’s calming pathways and human clinical trials showing anxiety-reducing effects.¹ What makes the science interesting is that these herbs don’t all work the same way. They calm the nervous system through at least four distinct mechanisms, and understanding which pathway a given herb acts on helps explain why some feel sedating, others feel more like stress resilience, and why mixing certain herbs with medications can be risky.

Herbs That Boost the Brain’s Own Braking System

The largest group of calming herbs works through the GABA system, your brain’s primary “slow down” signal. When GABA activity increases, neurons fire less, and the subjective experience is calm, drowsiness, or reduced anxiety. Several well-known herbs tap into this system, though each does it a bit differently.

Valerian root is one of the most studied. Its key compound, valerenic acid, slows the enzymatic breakdown of GABA in the brain, effectively letting more of the neurotransmitter hang around and do its calming work.² This is a different strategy from a drug like a benzodiazepine, which forces GABA receptors open more forcefully. Valerian works with whatever GABA your brain is already producing and just keeps it active longer, which may explain why its effects feel gentler.

Passionflower takes a more direct route. Lab studies show that extracts of Passiflora incarnata actually contain GABA itself as an ingredient, and when applied to brain tissue in the lab, they trigger GABA receptor currents that can be blocked by a GABA receptor antagonist, confirming the effect is genuinely receptor-mediated.³ Beyond delivering GABA directly, passionflower extract also inhibits the reuptake of GABA into nerve cells and binds to both GABA-A and GABA-B receptors.⁴ So it’s hitting multiple points in the same pathway at once.

Chamomile’s calming reputation comes largely from apigenin, a flavonoid that binds to benzodiazepine receptors and reduces GABA-activated nerve cell activity. The binding is real enough that it gets blocked by a standard benzodiazepine antagonist, which is the pharmacological equivalent of confirming the lock-and-key mechanism.⁵ A semi-synthetic derivative of chamomile was even found to be roughly 30 times more potent than diazepam at the benzodiazepine receptor, though that doesn’t mean chamomile tea hits you like a Valium; the naturally occurring concentrations are much lower.

Lemon balm works through yet another angle. Rosmarinic acid, which makes up about 1.5% of dried lemon balm leaves, potently inhibits GABA-transaminase, the enzyme that breaks down GABA. In lab assays, the crude extract showed about 40% inhibition of this enzyme.⁶ The mechanism parallels valerian’s, since both ultimately mean more GABA sticks around, but the active compounds are completely different.

Skullcap rounds out this group. Wogonin, isolated from Scutellaria baicalensis, binds to the benzodiazepine site on GABA-A receptors and enhances GABA-activated currents in neurons. Its effect gets partially reversed by the standard benzodiazepine antagonist flumazenil, which confirms it works through the same receptor site as pharmaceutical anti-anxiety drugs.⁷

Lavender Works Differently Than You’d Think

Most people associate lavender with relaxation through scent, but the herb also has a well-characterized pharmacological mechanism when taken as an oral supplement. Rather than acting on GABA receptors, lavender oil inhibits voltage-dependent calcium channels in nerve cells. Calcium flowing into neurons is part of what triggers them to fire and release excitatory neurotransmitters. By reducing that calcium influx, lavender turns down the overall excitability of neural circuits. Researchers found that lavender oil inhibits several types of calcium channels, including N-type, P/Q-type, and T-type, and does so in the same potency range as pregabalin, a pharmaceutical prescribed for anxiety and nerve pain.⁸

A standardized lavender oil preparation called Silexan has been studied more closely, and the profile is slightly different from pregabalin. While pregabalin mainly targets P/Q-type channels through a specific binding subunit, Silexan primarily inhibits T-type and N-type channels and has a more moderate effect on P/Q-type channels.⁹ This distinction matters because the different channel subtypes are found in different brain regions and serve different functions, which may help explain why lavender’s calming effect feels qualitatively different from that of GABA-acting herbs.

Adaptogens That Dial Down the Stress Response

A separate category of calming herbs works not by sedating the brain directly but by dampening the body’s stress-hormone machinery. These are the adaptogens, and their main target is the HPA axis, the chain of signals running from your brain to your adrenal glands that controls cortisol output.

Ashwagandha is the most heavily studied in this group. In a randomized, placebo-controlled trial, participants taking a standardized ashwagandha root extract showed greater reductions in morning salivary cortisol and increases in urinary serotonin compared to placebo.¹⁰ A separate trial found that ashwagandha reduced both morning cortisol and DHEA-S, a related adrenal hormone, suggesting the herb moderates HPA axis reactivity so the stress response doesn’t fire as hard or as long.¹¹ A review of the broader evidence concluded ashwagandha can normalize adrenal activity and reduce cortisol levels through effects on the HPA axis.¹²

Holy basil (Ocimum tenuiflorum, also called tulsi) acts on the same axis but through more specific mechanisms. In a placebo-controlled human trial, participants taking holy basil extract had lower salivary cortisol and salivary alpha-amylase concentrations in response to acute stress, along with lower blood pressure and lower subjective stress ratings. Their hair cortisol was also lower, suggesting the herb dampens HPA axis activity over weeks, not just in the moment.¹³ At the molecular level, holy basil and its constituents have been shown to inhibit cortisol release and block the CRH receptor (the first domino in the HPA cascade), which is a more upstream intervention than most pharmaceutical anxiolytics attempt.¹⁴ Animal studies have confirmed this: rats given holy basil extract maintained normal corticosterone levels despite being subjected to significant stress.¹⁵

Rhodiola rosea has a long history of traditional use for stress-induced fatigue and depression, and modern clinical evidence mostly supports its effects on cognitive function, mental performance, and fatigue symptoms during periods of life stress.¹⁶ A broader review of adaptogens, including rhodiola, found evidence of neuroprotective, anti-fatigue, and anxiolytic activity linked to regulation of stress mediators like cortisol and nitric oxide, as well as molecular chaperones that protect cells under stress.¹⁷ Adaptogens like rhodiola tend to feel less sedating than GABA herbs. They don’t necessarily make you sleepy; they make stressful situations feel more manageable.

Kava Is the Strongest, With the Biggest Caveats

Kava (Piper methysticum) deserves its own discussion because it’s probably the most potent herbal anxiolytic available, and also the most pharmacologically complex. Its primary active compounds, the kavalactones, work through multiple mechanisms simultaneously: they modulate GABA activity by altering lipid membrane structure and sodium channel function, inhibit monoamine oxidase B, and block noradrenaline and dopamine reuptake.¹⁸ The major kavalactone kavain has been shown to enhance GABA-A receptor activity regardless of subunit composition, though it does so without binding to the classical benzodiazepine site, which means its mechanism is distinct from both benzodiazepines and herbs like chamomile or skullcap.¹⁹

The catch is safety. Before reports of apparent liver toxicity emerged, kava was one of the top ten selling herbal remedies in Europe and North America.²⁰ Some kavalactones also block calcium and sodium ion channels, which could lead to pharmacodynamic interactions with drugs that have similar properties. The hepatotoxicity question has been debated for two decades, and many researchers believe the liver cases were tied to poor-quality extracts using the wrong plant parts or solvents. Still, anyone considering kava should be aware that regulatory agencies in several countries have restricted its sale, and combining it with alcohol or other liver-taxing substances is unwise.

Inhalation Versus Ingestion

Many calming herbs, particularly lavender and chamomile, are used as essential oils rather than swallowed. This isn’t just a cultural preference; the delivery route changes how the active molecules reach the brain. When you inhale an essential oil, the volatile compounds take two separate paths. Some molecules land on the olfactory mucosa in the nose and send signals directly into brain regions involved in emotion and arousal. Others pass into the respiratory tract, get absorbed through the lungs into the bloodstream, and eventually reach the brain that way.²¹

The olfactory route is fast and can produce calming effects within minutes, which is why aromatherapy often feels almost immediate. But the concentrations reaching the brain via the nose are generally lower than what oral dosing achieves. For lavender specifically, where the calming mechanism involves blocking calcium channels in neurons, oral standardized preparations deliver higher and more consistent levels of the active linalool and linalyl acetate to the brain. If your goal is a quick mood shift during an anxious moment, inhaling works. If you’re looking for sustained, pharmacologically meaningful effects, oral forms are better studied.

How Herb-Drug Interactions Actually Happen

The calming herbs that work through GABA pathways can theoretically amplify the effects of pharmaceutical sedatives, benzodiazepines, and sleep medications, since both the herb and the drug are pushing in the same neurochemical direction. This isn’t hypothetical concern; it’s the predictable result of layering two substances that both increase GABA activity. If you’re taking any medication that makes you drowsy, adding valerian or passionflower to the mix could deepen sedation in ways that aren’t safe, especially if you drive or operate anything dangerous.

Beyond this pharmacodynamic stacking, some herbs alter how your liver processes other drugs. Valerian root preparations have been shown to inhibit CYP3A4, a liver enzyme responsible for metabolizing a huge proportion of common medications, from statins to certain blood pressure drugs to some antidepressants. Other cytochrome P450 enzymes tested were not affected by valerian.²² CYP3A4 inhibition means those drugs get cleared from your body more slowly, which effectively raises their concentration in your blood and increases the chance of side effects. Kava and several other calming herbs also interact with cytochrome P450 enzymes and drug transporters, and results across studies are sometimes contradictory, making it hard to predict individual responses.²³

The practical takeaway is straightforward: if you’re on prescription medication, especially anything metabolized by the liver or anything that affects mood, sleep, or anxiety, talk to a pharmacist before adding herbal supplements. Pharmacists are often more up to date on interaction databases than general practitioners, and the conversation takes five minutes.

The Gut Microbiome Connection

An emerging line of research suggests some calming herbs may work partly through the gut. Flavonoids, which are present in chamomile, lemon balm, passionflower, and many other plants, can alter the composition and diversity of gut bacteria. Those bacteria, in turn, produce metabolites that may be responsible for some of the anxiolytic and mood-regulating effects traditionally attributed to the herbs themselves.²⁴ This would help explain something that has puzzled researchers for years: why the calming effects of some herbs seem to build up over days or weeks of regular use, rather than kicking in immediately. If part of the effect depends on reshaping the microbial community in your intestines, that’s a slow process compared to a molecule binding directly to a brain receptor.

The evidence here is still early, and most of it is preclinical. But it opens a genuinely different way of thinking about herbal calm. Rather than imagining each herb as a mild drug that hits a single receptor, the reality may be that herbs interact with the nervous system at multiple levels simultaneously: directly through receptor binding, indirectly through the HPA axis, and at a deeper level through the microbiome. That complexity is part of why herbal effects are harder to standardize than pharmaceutical ones, and why two people can take the same chamomile extract and have noticeably different experiences.

Gotu Kola and Long-Term Brain Changes

Most calming herbs are discussed in terms of their acute effects on neurotransmitters or stress hormones. Gotu kola (Centella asiatica) does something different. In an animal study using a chronic stress model, rats given gotu kola extract showed increased levels of BDNF (brain-derived neurotrophic factor) protein and its receptor in the hippocampus, along with upregulation of a signaling pathway involved in neuronal growth and survival.²⁵ BDNF is sometimes called a “fertilizer for neurons” in pop-science writing, and while that’s an oversimplification, the basic idea holds. Higher BDNF levels are associated with better stress resilience, and chronically low BDNF levels are a feature of anxiety and depression.

This is a completely different mechanism from the acute GABA or cortisol effects of the herbs discussed earlier. It points toward structural changes in the brain that could, theoretically, make a person more resilient to stress over time rather than just calmer in the moment. The evidence is still limited to animal models, so it would be premature to recommend gotu kola specifically for this purpose. But the finding illustrates why the question “what herbs calm the nervous system?” doesn’t have a single-mechanism answer. Some herbs turn down the volume on today’s anxiety. Others may be remodeling the circuits that process stress in the first place.

Why Cannabidiol Keeps Coming Up

CBD, derived from cannabis, is technically not a traditional herb in the way valerian or chamomile are, but it appears in virtually every modern conversation about herbal calming agents. Its mechanism is distinct from every herb discussed so far. In animal studies, CBD reduced both the physical and emotional components of the stress response, and this effect was mediated by serotonin 5-HT1A receptors rather than GABA or the HPA axis.²⁶ This makes CBD mechanistically more similar to certain antidepressants than to the sedative herbs in the GABA category.

The practical landscape around CBD is muddled by inconsistent product quality, varying legal status, and a flood of commercial hype that far outpaces the clinical evidence. Human trials for anxiety exist but tend to be small and variable in design. If you’re drawn to CBD for calming purposes, the serotonin pathway it works through suggests it may pair differently with medications than GABA herbs do, which is worth discussing with a healthcare provider. And since CBD is also known to interact with liver enzymes involved in drug metabolism, the same caution about checking for interactions applies.