Sleeping less than five hours at night increases the risk of depressive symptoms. It has been shown that people who sleep five or fewer hours per night are 2.5 times more likely to develop depressive symptoms.
A new study by experts at University College London (UCL) examined the connection between sleep duration and depression. The results have been published in the journal “Translational Psychiatry”.
Which occurs first?
Sub-optimal sleep duration and depression often occur together and, according to the team, represent a process of mutual influence. Even if short and long sleep are considered symptoms of depression, it is still unclear whether sleep problems promote depression or whether people with depression are more likely to develop sleep problems.
Until now, lack of sleep has been viewed as a side effect of mental illness, but the results of the current study show that the connection between sleep and mental illness is much more complex.
Data from 7,146 participants analyzed
For their study, the researchers analyzed data from a total of 7,146 people aged 50 and over, which came from the so-called English Longitudinal Study of Aging (ELSA). It was shown that short sleep duration is associated with the occurrence of depressive symptoms.
The study combined data on sleep and depressive symptoms from two ELSA surveys conducted two years apart because sleep duration and depression fluctuate over time.
The participants slept an average of seven hours per night. However, at the start of the study there was a proportion of more than ten percent of participants who slept less than five hours per night.
At the end of the study, more than 15 percent of the participants were found to be sleeping less than five hours per night. The proportion of participants who were classified as depressed increased by around three percentage points from 8.75 percent to 11.47 percent, the researchers report.
Poor sleep precedes depressive symptoms
“We have this chicken-or-egg scenario between suboptimal sleep duration and depression. They often occur together, but which occurs first is largely unresolved. Based on genetic susceptibility to disease, we found that sleep likely precedes depressive symptoms and not the other way around,” explains study author Odessa S. Hamilton in a press release.
The team found that people with a stronger genetic predisposition to short sleep, which is less than five hours of sleep per night, had a higher risk of developing depressive symptoms within four to 12 years.
In contrast, people who had a stronger genetic predisposition to depression had no increased risk of sleeping less than five hours per night, the researchers added.
“Short and long sleep durations as well as depression are important factors for the burden on public health that are highly heritable,” explains study author Dr. Olesya Ajnakina.
2.5 times increased risk of depressive symptoms
The experts also examined non-genetic connections between depressive symptoms and sleep duration. They found that people who slept five hours or less were 2.5 times more likely to develop depressive symptoms.
In addition, it was found that people with depressive symptoms were a third more likely to suffer from short sleep.
- How much sleep optimally protects against illness?
- Health risks caused by incorrect sleep duration
- Increase life expectancy by years with healthy sleep
Sleeping too long also promotes depressive symptoms
The researchers also identified a connection between long sleep times and the development of depressive symptoms. Participants who slept more than nine hours had a 1.5 times higher risk of depressive symptoms than people who slept an average of seven hours.
However, four to twelve years later, no connection between depressive symptoms and longer sleep duration could be identified, the team reports. This is consistent with the genetic results found. (as)