In a study of more than 2,000 British young adults, researchers from King's College London found that those who were lonely reported poor sleep quality.
For the analysis, loneliness was defined as a distressing feeling people experience when they perceive their social relationships to be inadequate.
While the effect of being lonely is well documented among the elderly, it is increasingly a common problem for young people, with the Mental Health Foundation reporting loneliness is most frequent in those aged 18-34.
According to the research team, lonelier people were 24 per cent more likely to feel tired and have difficulty concentrating during the day.
"Diminished sleep quality is one of the many ways in which loneliness gets under the skin, and our findings underscore the importance of early therapeutic approaches to target the negative thoughts and perceptions that can make loneliness a vicious cycle," explained Professor Louise Arseneault.
Diminished sleep quality includes struggling to fall asleep, stay asleep and daytime dysfunction such as staying awake during the day. Restless sleep in lonely individuals may also be due to feeling less safe or a result of a heightened biological stress response.
The study also found that the association between loneliness and poor sleep quality was almost 70 per cent stronger among those exposed to the most severe forms of violence, including crime, sexual abuse, child maltreatment and violent abuse by family members or peers.
"Sleep is a state in which it is impossible to be vigilant for one's safety, so feeling isolated from others could make it more difficult to sleep restfully, and even more so for individuals who have been exposed to violence in the past," explained researcher Timothy Matthews.
"It is therefore important to recognise that loneliness may interact with pre-existing vulnerabilities in some people, and that these individuals should receive tailored support."
The full study has been published in Psychological Medicine.
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