Brain areas associated with short-term memory, self and negative emotions are linked with depression which may cause the patients to dwell on bad thoughts and experience poor sleep quality, suggests a study.

According to the researchers, about 75 per cent of people with depression report significant levels of sleep disturbance, such as difficulty of falling asleep and short duration of sleep -- also known as insomnia. People with insomnia also have a higher risk of developing depression and anxiety than those who sleep normally.

"The understanding that we develop here is consistent with areas of the brain involved in short-term memory, the self, and negative emotion being highly connected in depression, and that this results in increased ruminating thoughts which are at least part of the mechanism that impairs sleep quality," said Jianfeng Feng, from the University of Warwick in Britain.

For the study, published in the journal JAMA Psychiatry, the team examined the neural mechanisms underlying the relation between depression and quality of sleep from around 10,000 people. They found a strong connection between the dorsolateral prefrontal cortex -- associated with short-term memory -- the precuneus -- associated with the self -- and the lateral orbitofrontal cortex -- associated with negative emotion-- among people with depression.

Increased functional connectivity between these brain regions provides a neural basis for how depression is related to poor sleep quality. "These findings provide a neural basis for understanding how depression relates to poor sleep quality, and this in turn has implications for treatment of depression and improvement of sleep quality because of the brain areas identified," Feng explained.