NPY and depressive symptom measurement: NPY is decisively involved in modulating the stress response systems like the hypothalamic–pituitary–adrenal axis system and, thereby, in the regulation of stress and anxiety, trauma-induced disorders, depression, chronic fatigue syndrome, cognition, learning and memory, information handling, neuroprotection, circadian rhythm, energy homeostasis, food intake, sexual behavior, migraine, epilepsy, schizophrenia, alcoholism, and addiction (10, 11).