Sleep terror, also referred to as night terror, is an episode of sudden extreme fright and panic during the night. The individual is abruptly awakened from sleep and emits a piercing scream. Yelling and incoherent verbalizations are common, but the individual is amnestic for the event. Sleep terrors usually occur during the first hour of sleep that is, during the first non-REM stage of sleep. The longer into the non-REM phase, however, the more severe the episode. The episodes last for no more than 10 or 15 min, at which time heart rate is in excess of 160 beats per min.