24 hours of sleep deprivation can lead healthy people to a condition similar to the symptoms of schizophrenia, which could serve as a model system for the development of drugs to treat psychosis.

In psychosis, there is a loss of contact with reality and this is associated with hallucinations and delusions. The chronic form is referred to as schizophrenia, which likewise involves thought disorders and misperceptions. Affected persons report that they hear voices, for example.

An international team of researchers has found out that after 24 hours of sleep deprivation in healthy patients, numerous symptoms were noted which are otherwise typically attributed to psychosis or schizophrenia. "It was clear to us that a sleepless night leads to impairment in the ability to concentrate," says Prof. Ulrich Ettinger, psychologist at the University of Bonn. "But we were surprised at how pronounced and how wide the spectrum of schizophrenia-like symptoms was."

The study was small, a total of 24 healthy subjects of both genders aged 18 to 40 in the sleep laboratory of the Department of Psychology. In an initial run, the test subjects were to sleep normally in the laboratory. About one week later, they were kept awake all night with movies, conversation, games and brief walks. On the following morning, subjects were each asked about their thoughts and feelings. In addition, subjects underwent a measurement known as prepulse inhibition.

Unselected information leads to chaos in the brain

"Prepulse inhibition is a standard test to measure the filtering function of the brain," explained lead author Dr. Nadine Petrovsky. In the experiment, a loud noise is heard via headphones. As a result, the test subjects experience a startle response, which is recorded with electrodes through the contraction of facial muscles.

If a weaker stimulus is emitted beforehand as a "prepulse", the startle response is lower. "The prepulse inhibition demonstrates an important function of the brain: Filters separate what is important from what is not important and prevent sensory overload," says Petrovsky.

This filtering function of the brain was significantly reduced following a sleepless night.

"There were pronounced attention deficits, such as what typically occurs in the case of schizophrenia," reports Ettinger. "The unselected flood of information led to chaos in the brain." Following sleep deprivation, the subjects also indicated in questionnaires that they were somewhat more sensitive to light, color or brightness. Accordingly, their sense of time and sense of smell were altered and mental leaps were reported.

Many of those who spent the night even had the impression of being able to read thoughts or notice altered body perception. "We did not expect that the symptoms could be so pronounced after one night spent awake," says the psychologist from the University of Bonn.

Sleep deprivation as a model system for mental illnesses

The scientists see an important potential application for their results in research for drugs to treat psychoses. "In drug development, mental disorders like these have been simulated to date in experiments using certain active substances. However, these convey the symptoms of psychoses in only a very limited manner," says Ettinger.

Sleep deprivation may be a much better model system because the subjective symptoms and the objectively measured filter disorder are far more akin to mental illnesses. Of course, the sleep deprivation model is not harmful: After a good night's recovery sleep, the symptoms disappear. There is also a need for research with regard to persons who regularly have to work at night. "Whether the symptoms of sleep deprivation gradually become weaker due to acclimatization has yet to be investigated," he says.