Yawning: Why and What Could It Mean?

Chemical causes:
 Androgens (like testosterone), oxytocin, and some medications like Prozac and other antidepressants can increase your frequency of yawning.Still, low oxygen levels in the paraventricular nucleus (PVN) of the hypothalamus of the brain can induce yawning. ... It contains a number of chemical messengers that can induce yawns, including dopamine, glycine, oxytocin and adrenocorticotropic hormone (ACTH).These chemicals include serotonin, dopamine, glutamic acid, and nitric oxide. As more (or fewer) of these compounds are activated in the brain, the frequency of yawning increases.