Passion Flower is traditionally used in Herbal Medicine as a sleep aid (in cases of restlessness or insomnia due to mental stress).
Passion Flower - Easing Your Way to Restful Sleep
A beautiful climbing plant that thrives in tropical and subtropical regions, passion flower was introduced to Europe from the Americas by the Spanish in the 16th century. From the outset, it was recognized for its remarkable tranquilizing and sedative properties.
Recent studies suggest quite strikingly that passion flower is as effective as pharmaceutical drugs (i.e. benzodiazepines) in eliminating the symptoms of anxiety-related disorders. In this vein, it is also quite useful in the treatment of insomnia, the great thing about it being that it does not cause any next-day hangover.