A key feature of insomnia is twenty-four-hour hyperarousal, which is characterized by chronic activation of both limbs of the stress system (i.e., the hypothalamic–pituitary–adrenal axis (HPA) and the sympathetic system), hypersecretion of adrenocorticotropic hormone (ACTH) and cortisol [13,14], elevated metabolic rates [15], and greater global cerebral glucose metabolism during nighttime and wakefulness [16,17,18]. The gene discussed is POMC; the disease is insomnia.