A method of affecting sleep and sleep-related behaviors of a mammal having a diurnal rhythm, by reducing the basal activity of the hypothalamus-pituitary-adrenal axis by administering an effective amount of a sensory regimen is disclosed. Such reduction may be accomplished by reducing at least one of the following: a. the average total daily amount of adrenocortical hormone; or b. the average total daily amount adrenocortical hormone minus the integrative measure of morning peak adrenocortical hormone. Preferably, such reduction also includes reducing at least one of the following: c. the level of adrenocortical hormone 4 hours to 8 hours after waking; d. the level of adrenocortical hormone in the period of time preceding bedtime; or e. the level of adrenocortical hormone below the onset of sleep threshold.