Hops and Stress: What a Small Crossover Trial Found

Hops (Humulus lupulus) is best known as a beer ingredient, but the same plant compounds have a real pharmacology — the strobile (flower) extract has been studied for calming, sedative effects independent of alcohol. It's also one of the ingredients in Proco's Sleep Support blend. Here's what the actual trial evidence shows.

Long before anyone put hops through a randomized trial, European herbal tradition had already claimed it: dried hop cones stuffed into pillows, hop tea taken as a folk sleep aid, and — per brewing lore — hop-pickers said to nod off in the fields from handling the flowers all day. That history is likely why researchers thought to test hops for sleep and calming effects in the first place. But tradition isn't evidence. A hop pillow was never a controlled experiment. What follows is what's actually been measured.

The trial

A randomized, double-blind, placebo-controlled crossover trial run at Harokopio University in Athens, Greece, gave healthy young adults a hops dry extract (two 0.2g capsules taken together in the evening, 0.4g daily) for two 4-week periods, separated by a 2-week washout. Of 126 adults screened with the DASS-21, 42 met the inclusion criteria and 36 completed both intervention periods (31 female, 5 male; mean age 24.7). Anxiety, depression and stress were measured using the DASS-21, a standard self-report scale.¹

What it found

All three DASS-21 subscales improved on hops relative to baseline, and hops beat placebo on all three. Anxiety fell from 9.2 to 5.1 (p = 0.003 against baseline; p = 0.009 against placebo), depression from 11.9 to 9.2 (p < 0.001; p = 0.001 vs placebo), and stress from 19.1 to 11.6 (p = 0.003; p = 0.009 vs placebo).¹ Body weight, body composition and morning circulating cortisol did not change with hops or placebo — the effect showed up in how people rated their own state, not in a measured stress hormone. That last point cuts both ways: it's honest that no biomarker moved, and it also means the entire result rests on self-report in an unblinded-to-yourself sense, since participants could plausibly notice a capsule's effects.

How hops might work

Hops contains two main classes of compounds researchers have looked at for central nervous system effects: bitter acids (alpha-acids like humulone, beta-acids like lupulone) and prenylated flavonoids, most notably 8-prenylnaringenin and its close relative 6-prenylnaringenin. 8-Prenylnaringenin is actually better known for a different reason — it's one of the most potent phytoestrogens ever identified in a plant — but several of these same compounds have also been screened for activity at GABA-A receptors, the same receptor system benzodiazepines, alcohol and z-drugs act on to produce calming and sedative effects.

A 2020 laboratory study testing hops compounds against rat GABA-A receptors found that humulone and 6-prenylnaringenin were the most potent modulators, positively enhancing GABA's inhibitory signaling at low micromolar concentrations — a mechanism consistent with a calming effect.³ Interestingly, the effect persisted even when the researchers added flumazenil, a drug that blocks the classic benzodiazepine binding site — suggesting hops compounds may work on GABA-A receptors through a different route than drugs like diazepam, not simply mimicking them. Separately, older animal research raised a second, more speculative mechanism: a 2007 study in mice found that the body-temperature-lowering (hypothermic) effect of a hops extract was blocked by luzindole, a melatonin-receptor antagonist — hinting that hops compounds may have some activity at the same receptors melatonin binds to.⁴

Valerian's own evidence base is the largest of the three botanicals discussed here and also the messiest — we've gone through it in valerian root for sleep: what the research actually shows.

Is there other human trial evidence for hops?

Beyond the Athens crossover trial, dedicated human research on hops by itself is sparse. The one other notable randomized trial involving hops paired it with valerian: a 2005 multicenter, placebo-controlled, parallel-group trial published in the journal Sleep gave 184 adults with mild insomnia (110 women, 74 men; mean age 44.3) either a valerian-hops combination tablet (187mg valerian extract plus 41.9mg hops extract, two tablets nightly, n=59), diphenhydramine 25mg (the antihistamine used in most over-the-counter sleep aids, n=60), or placebo (n=65) for 28 days.²

Here is what it actually found, stated the way the paper states it. The authors' own summary is that "few group comparisons with placebo reached statistical significance." Valerian-hops reduced sleep latency by 9.5 minutes at week 4 against placebo's 3.9 minutes — a difference the paper describes as "nearly significant (P = .0795)," which means it did not reach significance. Sleep efficiency at week 2 rose 3.1% on valerian-hops, not significantly different from either other group, while diphenhydramine's 4.6% gain was significantly better than placebo's 2.5% (P = .039). The one comparison that came out clearly in favour of the herbal arm was a quality-of-life measure: the physical component score at week 4 (P = .028). Most sleep parameters improved in all three groups, placebo included. The authors concluded there was a "modest hypnotic effect," and that neither treatment produced rebound insomnia or serious side effects on discontinuation.

A two-ingredient trial can tell you the combination worked. It can't tell you which ingredient did the work.

That's the honest limit of the 2005 trial for our purposes: it's a real, published, placebo-controlled result, but because valerian and hops were dosed together, it can't isolate what hops contributed versus what valerian contributed. It's the same logic we apply to Sleep Support's own 14-ingredient blend later in this article — a combination result isn't the same evidence as a single-ingredient result, even when the combination works.

How hops compares to Sleep Support's other sleep botanicals

Sleep Support isn't just hops — it also contains valerian and passion flower, two botanicals we've written about separately. Here's how the trial evidence for each actually compares, based on the specific studies discussed in this article and in those posts.

Valerian has the largest cumulative evidence base of the three by trial count and total participants, but the authors of its own meta-analysis were candid that the underlying studies used inconsistent preparations and doses and that the pooled result showed signs of publication bias — more data hasn't necessarily meant cleaner data. Passion flower's strongest single trial is almost exactly the same size as hops' but notable for a different reason: it tested a plant extract directly against oxazepam, a real prescription benzodiazepine, in 36 outpatients with a clinically diagnosed anxiety disorder rather than healthy volunteers — 18 on passionflower (45 drops daily), 18 on oxazepam (30 mg daily), over 4 weeks. Both were effective, and no significant difference was observed between the two treatments at the end of the trial. Oxazepam acted faster; passionflower was associated with significantly fewer problems relating to impairment of job performance.⁶ (An earlier version of this article credited both arms with "roughly a 68% reduction in anxiety scores." We could not verify that figure against the published paper, so we've removed it rather than leave an unchecked number standing. Note also what an equivalence result in 36 people can and cannot show: with arms this small, "no significant difference" is weak evidence of similarity, not proof of it.) Hops, by contrast, has exactly one dedicated human trial, in healthy (not clinically anxious) young adults, that hasn't yet been repeated by an independent research group. Of the three botanicals discussed across Proco's blog, hops is honestly the thinnest-evidenced — not because the one trial it has is bad, but because it's the only one it has.

For the wider picture on where botanical sleep support sits relative to everything else, best non-melatonin sleep aids ranks what the research actually supports, and the science of deep sleep separates the mechanisms from the marketing.

The honest limits

This is one trial, in a small (n=36), young, mostly-female, healthy population — not older adults, not a clinical anxiety or depression sample, and not yet independently replicated by a different research group. The outcomes were self-reported, not clinician-assessed. That's a real, statistically significant signal, not proof at the level we'd want before making a standalone product claim — which is exactly why hops sits inside a multi-ingredient sleep blend rather than as its own dosed product.

Why it's in Sleep Support

Hops is one of the 14 botanicals in Sleep Support's 905mg proprietary blend, alongside valerian, passion flower, chamomile and others with their own evidence bases. Like the rest of that blend, hops is not individually dosed on the label, and we are not going to promise a date for changing that — the only product in our range with full per-ingredient disclosure is Sleep Formula, and if per-ingredient numbers are what you need, that is the one to look at. The trial evidence above is for hops on its own, at a specific dose; it doesn't tell us exactly what hops contributes at whatever amount is in Sleep Support's blend. We're publishing what the ingredient-level evidence actually shows so you can judge it for yourself, not implying the blend has been tested this way.

If stress rather than sleep is the problem you're actually trying to solve, the ranked evidence is in what actually works for anxiety and managing stress without medication — and on that list, a single 36-person botanical trial sits a long way down.

This article is for informational purposes only and is not medical advice. It is not intended to diagnose, treat, cure, or prevent anxiety, depression, or any other condition.

References

1. Kyrou I, Christou A, Panagiotakos D, et al. Effects of a hops (Humulus lupulus L.) dry extract supplement on self-reported depression, anxiety and stress levels in apparently healthy young adults: a randomized, placebo-controlled, double-blind, crossover pilot study. Hormones. 2017;16(2):171-180. Conducted at Harokopio University, Athens. link.springer.com/article/10.14310/horm.2002.1738
2. Morin CM, Koetter U, Bastien C, Ware JC, Wooten V. Valerian-hops combination and diphenhydramine for treating insomnia: a randomized placebo-controlled clinical trial. Sleep. 2005. pubmed.ncbi.nlm.nih.gov/16335333
3. Hops compounds modulatory effects and 6-prenylnaringenin dual mode of action on GABA-A receptors. 2020. pubmed.ncbi.nlm.nih.gov/32001220
4. Hypothermic effects of hops are antagonized with the competitive melatonin receptor antagonist luzindole in mice. 2007. pubmed.ncbi.nlm.nih.gov/17430638
5. Bent S, Padula A, Moore D, Patterson M, Mehling W. Valerian for sleep: a systematic review and meta-analysis. American Journal of Medicine. 2006. pubmed.ncbi.nlm.nih.gov/17145239
6. Akhondzadeh S, Naghavi HR, Vazirian M, et al. Passionflower in the treatment of generalized anxiety: a pilot double-blind randomized controlled trial with oxazepam. Journal of Clinical Pharmacy and Therapeutics. 2001. pubmed.ncbi.nlm.nih.gov/11679026

Related reading

• Inside Sleep Support: An Honest Breakdown
• Passion Flower for Anxiety and Sleep: What the Trials Show

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