Afraid of the dark? It's actually a fear of the NIGHT

Think you're scared of the dark? It might actually be the night you're frightened of instead. Researchers found that people were more scared when subjected to frightening noises and images at night than in the day - even if the room was light.

It's thought our bodies switch over to a more vigilant mode at night, which makes us more jumpy.

'The present study indicates that individuals are highly reactive to cues that signal potential threatening events at night,' the researchers from Southwest University in China said.

Millions of adults suffer from anxiety disorders where their constant worrying affects their daily lives.

Now, scientists have identified the area of the brain that controls fear, offering hope of a treatment for such disorders.

US researchers have described a ‘circuit’ that controls fearful memories and behaviour in the brains of mice, offering insight into how anxiety disorders may develop.

Associate professor Bo Li, who led the study at Cold Spring Harbour Laboratory (CSHL) in New York, said: ‘In our previous work, we discovered that fear learning and memory are orchestrated by neurons in the central amygdala.’

It is thought it could be controlled by a cluster of neurons that form the PVT, or paraventricular nucleus of the thalamus.

For the study, researchers recruited 120 women who were tested, on their own, in a windowless cubicle in one of four conditions - light in daytime, dark in daytime, dark at night-time and dark at night-time.

On a computer screen they were shown 100 fear-inducing images, such as an assault in progress, and 50 neutral images, such as household items.

They also listened to 100 fear-inducing sounds, such as screams, and 50 neutral sounds, such as a whirring fan.

The temperature of the rooms was strictly controlled and responses were measured using physiological data - such as sweating, assessed through a skin conductance test, and heart rate - as well as the women's own reports.

The researchers found that there was no difference in the responses to the neutral images and sounds between the day and night.

However, the fear-inducing images and sounds made the women more frightened at night than in the day.

The women responded to potential threats more effectively at night, while their attention to 'safe' situations remained unchanged.

Writing in the International Journal of Psychophysiology, the researchers suggested that our circadian rhythm - the 24-hour cycle of biological processes - influences our fear-sensitivity.

Because night would have been a much more dangerous time for our ancestors than today, we have evolved to more efficiently process threat-related information at night, to keep ourselves safe.

'The evidence presented here suggests that night may amplify fearful signals and increase fear responses through one of the most basic and primitive forms, and this fundamental function of checking whether an external stimulus is potentially dangerous has deep evolutionary roots,' they said.

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