Passiflora, commonly known as passionflower, has a long history of traditional use for its calming and sedative effects, particularly in supporting sleep and reducing anxiety. Scientifically, Passiflora species (notably Passiflora incarnata) have been investigated for their potential action on the GABAergic system. GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the central nervous system, and modulation of GABA receptors can produce anxiolytic and sedative effects.

Several in vitro and animal studies suggest that extracts of passionflower may increase GABA levels in the brain or act as GABA agonists, leading to reduced neuronal excitability. Some small-scale human clinical trials have found that Passiflora extracts can reduce symptoms of anxiety, improve sleep quality, and produce mild sedative effects, supporting its traditional use. However, these studies are generally limited by small sample sizes, short durations, and variability in extract preparations.

While there is enough preliminary scientific evidence to suggest Passiflora may support the GABA system and related functions, the overall quality and quantity of clinical research is modest. Therefore, it is rated as "scientific" with an evidence score of 3/5—indicating some scientific support, but with a need for larger, well-designed human trials to confirm efficacy and clarify mechanisms.