What is hypnagogic hallucination?
Hypnagogic hallucination is episodes of seeing and hearing things as one is falling asleep. These dreams can be frightening and can often cause a sudden jerk and arousal just before sleep onset. For example, you may see yourself falling and awaken with a sudden jerk, just before impact. As the subject drifts off to sleep, he/she moves into a state that
combines the environment, of which the subject is still partially aware, with a dream-like state of sleep, in which he might see people and hear them talking. The experiences are often frightening. Sleep deprivation, irregular sleep schedules, and medications all can predispose to occurrences of this phenomenon.
Hypnagogic hallucinations can occur at sleep onset, either during daytime sleep episodes or at night. They are usually quite vivid, and often involve vision. The visual hallucinations usually consist of simple forms – colored circles or parts of objects – that are constant or changing in size. People may also see the image of an animal or a person, and are more often in color. Auditory hallucinations are also common, but other senses are seldom involved. Hypnagogic hallucinations are dreams that intrude on wakefulness, which can cause visual, auditory, or touchable sensations. They occur between waking and sleeping, usually at the onset of sleep, and can also occur about 30 seconds after a cataleptic attack. Hypnagogic hallucinations are a feature of narcolepsy.