Methods of treating depression, binge eating disorder, narcolepsy, excessive daytime sleepiness, substance use disorders, and Prader Willi syndrome, disorders characterized at least in part by hypocortisolemia and decreased activity of the hypothalamic-pituitary-adrenal (HPA) axis, and disorders related to disturbances in circadian rhythm, comprising the step of administering an effective amount of a histamine type 3 (H3) receptor antagonist, such as betahistine or its pharmaceutically acceptable salts, or its metabolites to an individual.
