Hope has today been raised for millions of people battling depression who find it difficult to sleep at night.
For researchers have finally discovered the reason why the blues can affect sleep quality after 100 years of mounting evidence.
Warwick University scientists found brain regions linked with short-term memory, self and negative emotions are strongly connected in depression.
They claim this may lead to poor sleep quality, such as struggling to get to sleep, by causing sufferers to dwell on bad thoughts.
Professor Jianfeng Feng, who led the trial, hopes it will open up new avenues of treating depression’s sleep side effects through new therapies or pills.
For researchers have finally discovered the reason why the blues can affect sleep quality after 100 years of research
He said: ‘The relation between depression and sleep has been observed more than one hundred years.
‘And now we have identified the neural mechanisms of how they are connected for the first time.
‘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.’
Around 216 million people around the world have depression, including three million in the UK and more than 16 million in the US.
Depression and sleep problems often go hand in hand.
Charities estimate three quarters of depressed patients have difficulty falling asleep, or often wake during the night.
Brain scans of 10,000 depressed people were taken for the new study, published in the JAMA Psychiatry.
Professor Feng and colleagues examined the neural mechanisms underlying the relation between depression and sleep quality.
In the brains of those living with depressive problems, they discovered a strong connection between three key regions.
The first was the dorsolateral prefrontal cortex – an area of the brain heavily linked with associated with short-term memory.
The others were the precuneus -associated with the self, and the lateral orbitofrontal cortex – which controls negative emotions.
Professor Feng said: ‘This results in increased ruminating thoughts which are at least part of the mechanism that impairs sleep quality.’
The Warwick team were helped in the research by scientists from Fudan University in Shanghai, China.
It follows a study in April that found eating raw carrots and spinach can boost ward off depression because they contain more ‘essential’ nutrients.
Scientists said raw vegetables – and fruit – are better for mental health than those which are cooked, tinned or processed.
Health campaigns have traditionally focused on the amount of fruit and vegetables people should eat, such as the five a day message.
But the study, by researchers in New Zealand, implies that the way in which they are prepared is also important to consider.