Nearly half of Britons regularly hallucinate, according to a study by Robert Priest, emeritus professor in psychiatry at the University of London.
In a survey of 5,000 people, Professor Priest found that 37 per cent experience hypnagogic hallucinations - vivid perceptual experiences in the moments before falling asleep - and 12.5 per cent experience hypnopompic hallucinations, similar experiences that occur at the time of awakening.
The most common hallucination is the feeling of falling into an abyss, followed by the sensation that someone or something is in the room. Other hallucinatory experiences include flying, seeing moving and distorted objects being on the receiving end of an attack and getting caught in a fire.
Women are significantly more likely to experience hallucinations than men (41 per cent and 30.6 per cent respectively) and far more younger people report experiencing these surreal phenomena than older subjects (44 per cent of 15 to 44 year olds compared with 24.6 per cent of those aged 65 and over).
Reading, engaging in intellectual activities and drinking alcohol in bed before going to sleep are all associated with hypnagogic hallucinations, says Professor Priest. There is also a link with smoking, light or agitated sleep, insomnia and daytime sleepiness.
"This is the first time that we have seen just how many people experience these types of hallucination," said Professor Priest. "People who are not psychotic or schizophrenic and who might be embarrassed or worried about hallucinating should feel reassured that they are not weird and their behaviour is quite normal."