They can't predict when an attack will occur, and many develop intense anxiety between episodes, worrying when and where the next one will strike. In between times there is a persistent, lingering worry that another attack could come any minute. Your hands may tingle or feel numb, and you might feel flushed or chilled. You may have chest pain or smothering sensations, a sense of unreality, or fear of impending doom or loss of control. You may genuinely believe you're having a heart attack or stroke, losing your mind, or on the verge of death.
Attacks can occur any time, even during nondream sleep.
While most attacks average a couple of minutes, occasionally they can go on for up to 10 minutes. In rare cases, they may last an hour or more.