Passionflower (Passiflora incarnata) for anxiety: what controlled trials show

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Passionflower (Passiflora incarnata) is one of the better-studied gentle herbal anxiolytics, with small randomized trials in generalized anxiety, pre-procedural nerves, opiate withdrawal, and sleep. "Better-studied" is relative: the total number of randomized participants is modest, most trials run only days to weeks, the preparations differ widely from one study to the next, and several of the key trials come from a single research group. The honest summary is a plausible, mild, short-term calming effect — useful context for situational anxiety, not a substitute for treatment of a diagnosed anxiety disorder. Here is what the controlled trials actually show, and where the evidence runs out.

The proposed mechanism

Passiflora incarnata extracts contain flavonoids (including vitexin, isovitexin, and chrysin) and trace β-carboline alkaloids. In animal models these constituents appear to act on the GABA-A receptor system — the same broad target as benzodiazepines, but far weaker. That weaker, less specific action fits the clinical picture seen in humans: mild calming without the dependence, tolerance, or marked motor impairment of prescription sedatives. Mechanism alone proves nothing about clinical benefit, so the trials matter more than the pharmacology.

The generalized-anxiety pilot

The most-cited efficacy study is Akhondzadeh and colleagues' 2001 double-blind trial in 36 outpatients with DSM-IV generalized anxiety disorder, randomized to passionflower extract (45 drops/day) or oxazepam (30 mg/day) over four weeks [1]. Both groups improved significantly on the Hamilton Anxiety scale, with no statistically significant difference between them, and oxazepam acted faster early on. Notably, impairment of job performance was significantly more common with oxazepam. The authors framed this as evidence that passionflower works about as well as a low-dose benzodiazepine with less daytime impairment — but the trial had no placebo arm, only 18 patients per group, and has never been replicated at scale. It is suggestive, not conclusive.

Pre-procedural anxiety: the most reproducible signal

The tightest evidence is in the minutes-to-hours before surgery. Movafegh and colleagues (2008) randomized 60 ambulatory-surgery patients to oral Passiflora incarnata 500 mg or placebo 90 minutes before their operation; numerical anxiety-rating scores were significantly lower with passionflower (P < 0.001), with no difference in sedation, psychomotor test performance, or discharge time [2]. Aslanargun and colleagues (2011) ran a parallel design in 60 spinal-anesthesia patients and likewise found that passionflower blunted the pre-operative rise in State-Trait Anxiety Inventory scores without affecting psychomotor function, sedation level, or hemodynamics [3]. Two independent groups, the same direction of effect, clean designs — this is the most persuasive part of the literature, even though the absolute effect is modest and the setting is narrow. (A larger 2024 perioperative trial of a multi-herb calming tea found no separation from a pleasant placebo tea, a reminder that delivery format and expectation matter [7].)

Opiate withdrawal: an unusual adjunct

Akhondzadeh's group also tested passionflower as an add-on during detoxification: 65 men undergoing 14-day outpatient opiate withdrawal received clonidine plus either passionflower extract or placebo [4]. Both arms controlled the physical symptoms of withdrawal equally, but the passionflower-plus-clonidine group did significantly better on the mental symptoms of withdrawal. It is an interesting finding, but it is a single small trial, clonidine remains the active backbone, and passionflower has not entered any addiction-medicine guideline on the strength of it.

Sleep and the tea question

For sleep, Ngan and Conduit (2011) ran a double-blind crossover study in 41 healthy adults who drank a cup of passionflower tea or placebo tea nightly for a week [5]. Subjective sleep quality was rated significantly better during the passionflower week, but in the subset of 10 participants who underwent overnight polysomnography there were no significant changes in objective sleep architecture. The reasonable reading: a low-dose tea may nudge how rested people feel during ordinary fluctuations in sleep, but it is not a treatment for insomnia or any underlying sleep disorder.

What the Cochrane review concluded

The Cochrane systematic review of passionflower for anxiety disorders (Miyasaka and colleagues, 2007) found only two eligible randomized trials, totaling 198 participants, and concluded that the evidence was too sparse to draw any conclusion about efficacy [6]. It specifically called for larger trials comparing passionflower against placebo and against standard medications. The literature has grown a little since, but the core limitations the review identified — few trials, small samples, heterogeneous preparations — remain unresolved, and a later systematic review of Passiflora across neuropsychiatric uses reached a similarly cautious verdict [8].

Safety and practical considerations

Passionflower is generally well tolerated at the doses used in trials (commonly 250–800 mg/day of standardized extract, or the tea). Reported adverse effects are mostly mild — drowsiness, dizziness, and occasional gastrointestinal upset — and in the controlled trials rates were close to placebo [2][3][5]. Because its presumed mechanism is sedative, it should not be combined with alcohol, benzodiazepines, or other central-nervous-system depressants, and driving or operating machinery is best deferred until individual response is known. Safety in pregnancy and breastfeeding has not been established, and as with all botanicals, product quality and actual extract content vary between brands. Anyone with moderate-to-severe or persistent anxiety should be evaluated for evidence-based treatment rather than relying on a herbal alone.

Sources

1. Akhondzadeh S, Naghavi HR, Vazirian M, et al. "Passionflower in the treatment of generalized anxiety: a pilot double-blind randomized controlled trial with oxazepam." J Clin Pharm Ther, 2001;26(5):363-7. PMID 11679026.
2. Movafegh A, Alizadeh R, Hajimohamadi F, et al. "Preoperative oral Passiflora incarnata reduces anxiety in ambulatory surgery patients: a double-blind, placebo-controlled study." Anesth Analg, 2008;106(6):1728-32. PMID 18499602.
3. Aslanargun P, Cuvas O, Dikmen B, et al. "Passiflora incarnata Linneaus as an anxiolytic before spinal anesthesia." J Anesth, 2012;26(1):39-44. PMID 22048283.
4. Akhondzadeh S, Kashani L, Mobaseri M, et al. "Passionflower in the treatment of opiates withdrawal: a double-blind randomized controlled trial." J Clin Pharm Ther, 2001;26(5):369-73. PMID 11679027.
5. Ngan A, Conduit R. "A double-blind, placebo-controlled investigation of the effects of Passiflora incarnata (passionflower) herbal tea on subjective sleep quality." Phytother Res, 2011;25(8):1153-9. PMID 21294203.
6. Miyasaka LS, Atallah AN, Soares BGO. "Passiflora for anxiety disorder." Cochrane Database Syst Rev, 2007;(1):CD004518. PMID 17253512.
7. Zampieri VC, Gonçalves IL, Lira AL, et al. "Exploring the Effects of a Calming Herbal Tea Blend on Perioperative Anxiety: A Randomized Clinical Trial." J Med Food, 2025;28(3):266-271. PMID 39514279.
8. Janda K, Wojtkowska K, Jakubczyk K, et al. "Passiflora incarnata in Neuropsychiatric Disorders—A Systematic Review." Nutrients, 2020;12(12):3894. PMID 33352740.