"Many people confuse nightmares and night terrors," says Zadra, "but they're completely different conditions, and you don't need a sleep expert to help you tell them apart."
According to Zadra, night terrors, (or "sleep terrors" in the jargon of the pros) are characterized by the victim's obvious sense of panic and disorientation.
"Their eyes are open," he says, "their heart rate might triple, they might hyperventilate, they usually scream and they are always in extreme confusion."
It's a hallmark of the disorder, Zadra says, that sleep terror victims aren't able to identify the source of their panic; at best there's the lingering impression of a vague and frightening image — a burning house, being buried alive — but in the morning, the entire episode is often forgotten.
"We've had patients experience a full-blown attack in the lab," he says, "and not remember a thing in the morning. They're astounded when we show them the video."
On the other hand, Zadra says, sufferers of even the nastiest nightmares rapidly reorient themselves after awakening. "They tend to wake with a feeling of relief rather than confusion," he says. "They realize quickly that they were dreaming, and in the morning they can usually recall the entire dream."
The two conditions respond to differing treatments, too. Since sleep terror attacks seem linked to periods of stress, training in stress management techniques often helps to dramatically reduce the frequency and intensity of attacks.
A regular sleep schedule is also important, says Zadra, because it regulates the amount of time we spend in slow wave sleep each night. "Sleep terrors occur in deep, slow wave sleep," he explains. "If you are deprived of sleep, your body will make up for it by increasing the time you spend sleeping at those deep levels. And that widens the window for more sleep terror attacks."
"There are no real studies on the effectiveness of the treatment," says Zadra, "but in my experience, I'd say about half the people we treat report fewer, or less intense episodes, or both."