What Separates A Nightmare From A Night Terror

Two experiences are routinely described with the same words and are physiologically unrelated. Nightmares and night terrors occur in different stages of sleep and behave in almost opposite ways.

Where each one occurs in the night

Nightmares arise from dreaming sleep, which lengthens through the night, so they cluster in the second half and often occur shortly before waking in the early morning.

Night terrors arise from deep slow-wave sleep, which is concentrated in the first cycles, so they typically occur within the first few hours after falling asleep.

The timing alone is usually enough to distinguish them, and it is the first thing a clinician will ask about when a family describes frightening episodes at night.

What the person does

A nightmare ends in waking. The dreamer comes fully awake, is oriented, frightened, and generally able to describe what was happening in some detail.

A night terror does not involve waking at all. The person may sit up, scream, thrash or appear terrified while remaining asleep and unresponsive to attempts at comfort.

Attempting to wake someone in a night terror usually prolongs the confusion, which is why the standard advice is to keep them safe and let the episode run its course.

What is remembered afterwards

Nightmares are remembered, sometimes vividly and for years, and the memory is of a narrative with events, settings and characters in the ordinary dream fashion.

Night terrors leave little or nothing. The person typically has no recollection of the episode the next morning, and what fragments remain are usually a single image or feeling rather than a story.

This asymmetry means the distress from a night terror falls mostly on whoever witnessed it, which is a point worth making to alarmed parents.

Who experiences which

Night terrors are largely a childhood phenomenon, most common in early school years, and the great majority of children who have them outgrow them without any intervention.

Nightmares occur at every age, are common in childhood, and continue into adulthood, where their frequency varies considerably between individuals and across periods of life.

Night terrors run in families and share that tendency with sleepwalking and related behaviours, which are also disorders of partial arousal from deep sleep.

When either becomes a clinical matter

Frequency and consequence are what matter. Occasional episodes of either are unremarkable, and reassurance is generally the appropriate response.

Episodes that occur often, cause injury, produce fear of going to bed, or begin in adulthood after a period without them are reasons to consult a clinician.

Effective treatments exist for frequent distressing nightmares, and safety measures and attention to sleep timing help with arousal disorders, so neither should be endured as unavoidable.