• Posted October 23, 2023

Short Sleepers May Be at Higher Risk for Depression

Scientists have long wondered whether depression leads to less sleep or whether a lack of sleep triggers depression.

A new study suggests it's the latter: Getting less than five hours of sleep a night may raise the risk of developing depressive symptoms.

"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,"said lead author Odessa Hamilton, of University College London's (UCL) Institute of Epidemiology & Health Care.

Both sleep style and depression are partly inherited from one generation to the next. Earlier twin studies have suggested depression is about 35% genetic and that these inherited differences account for 40% of the variance in sleep duration.

In this latest study, the researchers analyzed genetic and health data from more than 7,000 people who were an average age of 65.

The investigators found that those with a stronger genetic predisposition to short sleep were more likely to develop depressive symptoms over four to 12 years.

Meanwhile, people with a greater genetic predisposition to depression did not have an increased likelihood of short sleep.

"Short and long sleep durations, along with depression, are major contributors to public health burden that are highly heritable," said senior study author Dr. Olesya Ajnakina, of UCL's Institute of Epidemiology & Health Care and the Institute of Psychiatry, Psychology & Neuroscience at King's College London.

"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,"Ajnakina said in a UCL news release.

The researchers assessed the strength of genetic predisposition among the participants using findings from previous genome-wide association studies. Those studied had identified thousands of genetic variants linked to a higher likelihood of developing depression and short or long sleep.

The team also wanted to be sure their results were robust, so they looked at non-genetic associations between depressive symptoms and sleep duration.

The findings showed that people sleeping five hours or less were 2.5 times more likely to develop depressive symptoms. People with depressive symptoms were one-third more likely to suffer from short sleep.

Interestingly, sleeping long -- more than nine hours a night -- was also linked to developing depressive symptoms. Individuals who slept long were 1.5 times more likely to develop depressive symptoms as those who slept an average of seven hours.

However, depressive symptoms were not associated with sleeping longer, according to the report.

"Suboptimal sleep and depression increase with age, and with the worldwide phenomenon of population aging 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,"said Andrew Steptoe, head of behavioral science and health at UCL's Institute of Epidemiology & Health Care.

The findings were published online Oct. 20 in the journal Translational Psychiatry.

More information

The U.S. National Heart, Lung, and Blood Institute has more on sleep.

SOURCE: University College London, news release, Oct. 19, 2023