Passionflower (Passiflora incarnata) is a flowering, woody vine traditionally used as a calming and sedative agent. The flower petals, leaves, and stems of the plant are typically used in supplements.^[7] People around the world have used it as a treatment for pain, insomnia, anxiety, and opioid dependence.^[8] The supplement comes in several formulations, including teas, capsules, tablets, and liquids. In addition to its uses as a supplement, passionflower is also a FDA-approved food additive for flavoring purposes.^[9]

The Passiflora genus has many different species. Passiflora incarnata should not be confused with Passiflora edulis; even though the latter has shown numerous effects in animal studies, very limited information is available regarding its use in humans.^[10]

Passionflower has been traditionally used for anxiety and insomnia, due to its calming and sedating effects.^[8] However, there is limited clinical data to support the use of passionflower for these purposes, and larger clinical trials should be conducted.

One study compared the effect of 45 drops/day of a branded passionflower extract (prepared from the standardized extract of leaves, flower and fruit of Passiflora Incarnata and containing 11–15 mg per 100 ml of total flavonoids as hyperoside^[11]) to oxazepam (a benzodiazepine used to treat symptoms of anxiety and insomnia) in reducing symptoms of generalized anxiety disorder. Results showed that passionflower decreased symptoms of anxiety, with a lower incidence of job performance impairment and dizziness than oxazepam.^[5] Two other studies compared passionflower to placebo in the anxiety-inducing situation of preoperative procedures. Both 500 mg of the same standardized passionflower extract used in the previous study and 750 mg of a Passiflora incarnata syrup resulted in a decrease in anxiety, compared to placebo, without causing sedation.^[1][2] Moreover, another study showed a decrease in anxiety symptoms and an increase in sedation when participants received either passionflower or midazolam before a dental procedure. Participants given passionflower also experienced limited memory loss associated with the procedure, in contrast to midazolam, which may cause temporary memory loss; however, this is not necessarily a positive, as some people may prefer not to remember medical procedures.^[12] Additionally, one study showed that passionflower may be a helpful add-on therapy to sertraline (a selective serotonin reuptake inhibitor, or SSRI) for anxiety.^[13] While these studies did show a reduction in anxiety levels, and an increase in sedation, associated with passionflower, more studies should be conducted to validate these results.

One study found that sleep quality was improved when drinking 2 grams of passionflower tea a day compared to placebo. However, the study did not find any differences in sleep onset, number of awakenings, feelings of refreshment upon awakening, or anxiety symptoms between the passionflower and placebo groups.^[3] It is worth noting that the passionflower dose used in this study was smaller than that used in other studies looking at anxiety outcomes. Furthermore, this study had a small sample size, was short in duration, and although the outcomes were measured through sleep diaries and polysomnography (PSG), the bulk of participants only provided sleep diaries; only ten people underwent PSG. Therefore, larger and longer studies should be conducted to better understand the impact of passionflower use on insomnia.

Passionflower is generally well-tolerated, but there are some side effects that have been found in clinical trials. Some common side effects of passionflower supplementation include dizziness, confusion, drowsiness, nausea, and vomiting.^[14][15] In rare but serious cases, passionflower has been shown to increase uterine contraction, causing the induction of labor;^[16] it should therefore not be used in pregnancy.^[17] Additionally, there has been one case report of increased heart rate, palpitations, and chest pain after taking passionflower supplements.^[18]

It is worth noting that clinical trials often look at passionflower in combination with other remedies, making it harder to determine its benefits as well as its side effects.

Passionflower appears to act on the gamma-aminobutyric acid (GABA) pathway system. By increasing levels of GABA, brain cell activity is decreased, leading to calming and sedating effects.^[19]

Passionflower also contains flavonoids^[8] that have anti-inflammatory and antioxidant properties, as well as indole alkaloids. The latter may be responsible for the antidepressant and anxiolytic effects of passionflower, although more research is needed to clarify their role.^[20]