Consistently sleeping less than five hours a night could increase the risk of depression, research suggests. Poor sleep has been considered a side-effect of mental ill health in the past, but the new study found that the link between sleep and mental illness is more complex. People with a stronger genetic predisposition to short sleep – less than five hours in a given night – were more likely to develop depressive symptoms over four to 12 years, the study led by UCL researchers found. But those with a greater genetic predisposition to depression were not more likely to have short sleep. Using genetic susceptibility to disease, we determined that sleep likely precedes depressive symptoms, rather than the inverse Lead author Odessa Hamilton The experts also found that the link was not exclusive to those who were genetically inclined towards sleeping for shorter periods, and people who regularly dozed for five hours or less – without the genetic association – were also more likely to have depression. Lead author Odessa Hamilton, UCL Institute of Epidemiology and Health Care, said: “We have this chicken or egg scenario between suboptimal sleep duration and depression, they frequently co-occur, but which comes first is largely unresolved. “Using genetic susceptibility to disease, we determined that sleep likely precedes depressive symptoms, rather than the inverse.” Researchers used genetic and health data from 7,146 people recruited by the English Longitudinal Study of Ageing (ELSA), with an average age of 65. Short and long sleep durations, along with depression, are major contributors to (the) public health burden that are highly heritable Senior author Dr Olesya Ajnakina Analysis of genetic and health data suggested that short sleep was associated with the start of depressive symptoms, like feeling sad or lonely. Senior author Dr Olesya Ajnakina, UCL Institute of Epidemiology and Health Care and the Institute of Psychiatry, Psychology and Neuroscience at King’s College London, said: “Short and long sleep durations, along with depression, are major contributors to (the) public health burden that are highly heritable. “Polygenic scores, indices of an individual’s genetic propensity for a trait, are thought to be key in beginning to understand the nature of sleep duration and depressive symptoms.” When looking at non-genetic associations between depressive symptoms and sleep duration, the researchers also found that people sleeping five hours or less were 2.5 times more likely to develop depressive symptoms. And people with signs of depression were a third more likely to suffer from short sleep. Suboptimal sleep and depression increase with age, and with the worldwide phenomenon of population ageing there is a growing need to better understand the mechanism connecting depression and a lack of sleep Professor Andrew Steptoe The study, published in Nature, Translational Psychiatry, also revealed a link between sleeping long and developing depressive symptoms. According to the findings, people who slept for more than nine hours were 1.5 times more likely to develop depressive symptoms than those who sleep an average of seven hours. However, depressive symptoms were not associated with sleeping longer four to 12 years later, which corresponded to the genetic findings. Professor Andrew Steptoe, head of Behavioural Science and Health, UCL Institute of Epidemiology and Health Care, said: “Suboptimal sleep and depression increase with age, and with the worldwide phenomenon of population ageing there is a growing need to better understand the mechanism connecting depression and a lack of sleep. “This study lays important groundwork for future investigations on the intersection of genetics, sleep, and depressive symptoms.” People enrolled in the study had an average of seven hours’ sleep a night. More than 10% slept for less than five hours a night at the start of the study period, rising to more than 15% at the end of the study. The proportion of people classed as having depressive symptoms increased by about three percentage points, from 8.75% to 11.47%. In the study, data on sleep and depressive symptoms were combined from two Elsa surveys conducted two years apart, as sleep duration and depression are known to fluctuate over time. Sleep duration and depression are both partly inherited from one generation to the next. Earlier studies have suggested depression is about 35% heritable, and that genetic differences account for 40% of the variance in sleep duration. Read More World Osteoporosis Day: The risk factors and early warning signs everyone needs to know about How to support a child with a stammer From colourful gowns to drones, these wedding trends are set take over 2024 Call The Midwife ‘should come with a health warning’ Halloween: 10 wicked ways to kit out your haunted house Black magic: Go back to black this season with the catwalk-inspired trend

If you want to cheat the system a bit and get your hands on incredible,

SAVE 49%: Watch the British Grand Prix for free with ExpressVPN. A one-year subscription to

Gazing up from K2 Basecamp, Sajid Ali Sadpara sees Earth's second-highest mountain, his father's final resting place, and a blight of litter on the furthest...

(Reuters) -Archer-Daniels-Midland beat Wall Street expectations for second-quarter profit on Tuesday, as the grain trader and processor benefited from tight

The web hosting world is large and varied, with many services competing for your trust

Venmo will officially allow teenagers to open an account with their parents' permission, the company said Monday, expanding the popular social payments app to a demographic that is likely to embrace it almost immediately

The Barbie script is genius. So genius in fact that for the past week I've

For many teens, roaming shopping malls, hanging out at amusement parks, and watching a movie at a local theater with their peers have been long considered the rites of passage to adulthood

June is shaping up to be a great month for fans of the creepy tech

Right from the jump, The Other Black Girl wants you to know that the workplace

Pretty much everything you see in this image is a galaxy — an entire galaxy