Derived from the aerial parts of the plant, passionflower is used by patients to treat insomnia, anxiety, epilepsy, neuralgia, and withdrawal syndromes from opiates or benzodiazepines. The alkaloid components (e.g., harman, harmaline) are thought to produce monoamine oxidase inhibition, while other constituents, like maltol and gamma-pyrone derivatives, cause activation of GABA receptors (1). Theoretically, passionflower may potentiate the sedative effect of centrally acting substances (e.g., benzodiazepines, barbiturates, alcohol) (2).
A small pilot study evaluated passionflower for generalized anxiety and showed comparable efficacy to oxazepam (3), but a systematic review concluded that randomized controlled studies are needed to confirm such effects (4). In patients undergoing surgery, preoperative passionflower use reduced anxiety (5) (16). However, one study found that administration of five different Passiflora incarnata extracts to mice in their drinking water produced anxiogenic effects. Two of these extracts did show an anticonvulsant effect against pentylenetetrazol-induced seizures (6).
Consumption of a low dose of passionflower tea affected short-term benefits in sleep quality in healthy adults (17).
When used concurrently, passionflower was shown to enhance the pharmocological effects of St. John's Wort (18).
Not all passionflower extracts are standardized because of which dosages and activities may vary.