NPY and psychiatric disorder: The determinants of mental health are neurotransmitters secreted in the brain like acetylcholine (ACh), epinephrine (adrenaline), dopamine, endorphins and enkephalins, gamma-aminobutyric acid (GABA), glutamate, neuropeptide Y, noradrenaline, oxytocin, phenylethylamine, serotonin (5-hydroxytryptamine, 5-HT), and substance P. There is also recent evidence that relates to neuroimmunomodulation and psychiatric disorders.