 Neuropeptide Y has been reported to reduce the release of norepinephrine and has been demonstrated to have anxiolytic properties in animal models.Studies have shown people with PTSD demonstrate reduced levels of NPY, possibly indicating their increased anxiety levels.Other studies indicate that people that suffer from PTSD have chronically low levels of serotonin, which contributes to the commonly associated behavioral symptoms such as anxiety, ruminations, irritability, aggression, suicidality, and impulsivity.