Passionflower: what the research does and doesn't show

Passionflower isn't studied for use during pregnancy in a controlled way. A small published case series in pregnant women who used it reported serious complications in some pregnancies, and a rat study found a behavioral effect in male offspring at a higher dose. No trial has tested passionflower for headaches, constipation or kids, and no research specifically documents diarrhea either.

What the evidence doesn't support

It doesn't support passionflower, in any form, as something to take during pregnancy or while breastfeeding — that's a hard caution based on limited human data and a documented animal signal, not a dosing question. It doesn't support passionflower for headaches, constipation, or use in children — none has been tested. And the case series and animal study below don't establish that passionflower caused the outcomes they describe; they're a reason for caution, not proof of harm.

What the research found

No controlled human study has tested passionflower during pregnancy. The closest human data is a published case series describing five pregnant women, each with a diagnosis of depression or anxiety, who used Passiflora incarnata while pregnant. Several of those pregnancies had serious complications: one ended in neonatal death, two involved premature rupture of membranes, two infants had meconium aspiration syndrome, and one infant had persistent pulmonary hypertension. No birth defects or developmental problems were reported in the surviving infants at six months. This is an uncontrolled report of five real-world cases, not a trial — the women's underlying psychiatric conditions, any other medications they may have taken, and the small sample all limit what can be concluded about passionflower specifically. The authors themselves noted that lab-based studies hadn't found the extract to cause birth defects, but that no human pregnancy data existed before their report, and recommended monitoring pregnant women who use it until more is known.

A rat study gave pregnant animals passionflower throughout pregnancy and early nursing at two doses. It found no effect on litter size, pup survival, or the pups' physical development at either dose. But at the higher dose, most adult male offspring showed disrupted sexual behavior compared with untreated controls — a finding not explained by a measurable change in testosterone or sperm count. That's an animal result at a dose well above typical human intake, using whole-plant material rather than a human-equivalent extract — it doesn't translate directly to a person, but combined with the case series above, it's a second, independent signal that passionflower during pregnancy and early development deserves caution rather than an assumption of safety.

No trial has tested passionflower for headaches or constipation, in any form. No trial has enrolled children or teenagers, and no dose has been established for anyone under 18.

On diarrhea specifically: no trial or case report documents it as an effect of passionflower. The one serious published case report describes a woman hospitalized with nausea, vomiting, drowsiness and an abnormal heart rhythm after a self-administered "therapeutic" dose — real, serious symptoms, but not diarrhea, and a single case rather than a measured rate.

A 2013 review of the published clinical literature on passionflower found that the trials evaluating its calming effects generally had real methodological weaknesses — small samples, unclear blinding, poorly described extracts — a reason to read any single positive result, including the ones covered on this site's other passionflower pages, with some caution.

Questions people ask

Is passionflower tea safe during pregnancy?

No controlled study has tested it. A published case series of pregnant women who used passionflower reported serious complications in some pregnancies, and a rat study found a behavioral effect in male offspring at a higher dose. Ask a doctor before using passionflower, in any form, during pregnancy.

Is passionflower safe while breastfeeding?

No controlled study has tested this either. Ask a doctor before using passionflower while breastfeeding.

Can passionflower cause headaches?

No trial has tested this. Headaches aren't reported as a measured outcome, positive or negative, in any published passionflower research.

Can passionflower cause diarrhea?

No trial or case report specifically documents diarrhea. The one serious case report on record describes nausea and vomiting, not diarrhea, alongside other symptoms — see passionflower side effects for the details.

Can passionflower cause constipation?

Not measured in any trial. This reflects an absence of research rather than a tested finding either way.

When to talk to a doctor

Persistent headaches, chronic digestive symptoms, or any symptom in a child are worth a doctor's evaluation rather than a supplement search — passionflower is not a treatment for any of them, and none has been tested. If you're pregnant, nursing, or considering passionflower for a child, talk to a doctor first; the case series and animal data above are reasons for caution, not an answer.

Related reading: who should not take passionflower, passionflower side effects, and passionflower benefits: what the research does and doesn't show.