Shakespeare's play 'Macbeth' suggested a link between sleeplessness and paranoid - with the insomniac title character increasingly becoming paranoid that it will be discovered that he had killed the king - and now his artistic theme has been seconded by a Wellcome Trust-funded study.
Published online in the journal 'Schizophrenia Research', the study suggests that increased suspiciousness is a potential consequence of insomnia.
This is the first time that any scientific research has examined insomnia and persecutory thoughts.
The study showed that, in the general population, individuals with insomnia were five times more likely to have high levels of paranoid thinking than those who were sleeping well.
During the study, over 50 per cent of the individuals attending psychiatric services for severe paranoia were found to have clinical insomnia.
Research leader Dr. Daniel Freeman, a Wellcome Trust Research Career Development Fellow at the Institute of Psychiatry, King's College London, has also written about the new science of suspiciousness in a new book titled 'Paranoia: The 21st-century fear'.
"As most of us know, a few nights of poor sleep can make us feel stressed, muddled in our thinking and disconnected from the world. These are ideal conditions for paranoid fears to take hold. Regular, good-quality sleep is important to our psychological wellbeing," Science Daily quoted Dr. Freeman as saying.
However, despite having confirmed a clear link between the two conditions, the researcher admits that it has yet to be established as to which one of them causes the other.
According to him, clinical experience indicates that there is a vicious cycle in which insomnia makes people anxious and fearful, and such feelings in turn make it harder for them to sleep.
Dr. Freeman believes that the research points to a potential treatment for helping to reduce the risk of developing persecutory thoughts.
"The good news is that there are several tried-and-tested ways to overcome insomnia. In particular, cognitive behavioural therapy (CBT) has proven benefits. The intriguing implication of the research is that use of the sleep techniques may also make us feel safer and less mistrustful during the day. A good night's sleep may simply make us view the world in a much more positive light," he says.