Guide
Passionflower side effects
The regulatory reference lists passionflower's side effects as none known but warns it may impair driving; a published case report describes a woman hospitalized after taking it at a self-described therapeutic dose.
The one regulatory reference on passionflower calls its side effects "none known," but adds two things worth noticing: it may impair the ability to drive or operate machinery, and a doctor should be consulted if a reaction happens. A published case report, separately, describes a woman hospitalized after taking it.
What the European Medicines Agency's monograph says
The EMA's 2014 traditional-use monograph lists undesirable effects as "none known," which reflects the traditional-use registration category — based on long-standing use rather than the kind of systematic safety monitoring a clinical drug trial runs — and directs that a doctor be consulted if any reaction occurs. The same monograph separately warns that passionflower may impair the ability to drive or use machines, and states that no case of overdose has been reported to it.
What the two human trials reported
The 2008 trial that gave adults a single 500 mg dose of Passiflora incarnata extract before surgery measured sedation directly, using a numerical rating scale and two psychomotor tests (the Trieger Dot Test and Digit-Symbol Substitution Test) — and found no significant difference from placebo on any of them. The 2011 tea trial's published results focus on sleep-quality ratings and don't report a side-effect count for either the tea or placebo group.
A published case report
A case report describes a 34-year-old woman who developed severe nausea, vomiting, drowsiness, a prolonged QTc interval (a heart-rhythm measurement) and episodes of a fast, abnormal heart rhythm after self-administering Passiflora incarnata at what she considered a therapeutic dose. The connection to passionflower wasn't recognized for several days, and she needed hospital admission for cardiac monitoring and intravenous fluids. One case report doesn't establish how common this is — it's the only published account of its kind — but it's a documented reason not to assume an herbal product is automatically low-risk.
Does passionflower make you sleepy?
The only trial that measured sedation directly — the 500 mg pre-surgery dose — found no significant difference in sedation scores between passionflower and placebo. That's one dose, in one trial. The plant itself is classified in a 2004 review as having documented central-nervous-system-depressant properties, and the EMA's own monograph warns it may impair driving and machine use, so a drowsy effect at some dose or form isn't out of the question — it just hasn't been measured and quantified the way that 500 mg trial dose was.
Questions people ask
Does passionflower tea have side effects?
No trial has reported a side-effect count specifically for the tea. The closest data point is the 500 mg extract trial, which found no added sedation, and the EMA's monograph, which lists undesirable effects as "none known" for the traditional-use category generally.
Can passionflower cause vivid dreams?
No trial has measured dream content or vividness. Reports of vivid dreams with passionflower are anecdotal, not something either of the two human trials tested for or reported.
What are the risks of passionflower?
Based on what's published: a documented case of significant adverse effects at a self-described therapeutic dose, a regulatory caution about impaired driving and machine use, and — separately — a suspected interaction with a sedating medication, covered in passionflower and medications: what to check.
Related reading: who should not take passionflower?, passionflower and medications: what to check, and how much passionflower should you take a day?.
Sources
- Toxicity of Passiflora incarnata L A published case report describes a woman hospitalized with nausea, vomiting, drowsiness and an abnormal heart rhythm after taking Passiflora incarnata at a self-described therapeutic dose.
- Preoperative oral Passiflora incarnata reduces anxiety in ambulatory surgery patients: a double-blind, placebo-controlled study A 2008 placebo-controlled trial found a single 500 mg dose of Passiflora incarnata extract, given 90 minutes before surgery, produced better anxiety scores in surgical patients than placebo, without added sedation or slower recovery.
- Passiflora: a review update A 2004 review of the Passiflora genus found P. incarnata has documented central-nervous-system-depressant properties in laboratory and animal research, and identified flavonoids as its major active compounds — not a human clinical trial.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.