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.[1][2] In rare but serious cases, passionflower has been shown to increase uterine contraction, causing the induction of labor;[3] it should therefore not be used in pregnancy.[4] Additionally, there has been one case report of increased heart rate, palpitations, and chest pain after taking passionflower supplements.[5]
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.