Little or bad sleep can be one of the consequences suffered by people who have a mental illness, but inadequate rest is also a risk factor for suffering from a psychiatric disorder, and now a genetic study has found that a chronic lack of sleep, Specifically, sleeping less than five hours a night on a regular basis could increase the chances of developing depressive symptoms.
The research has been led by scientists from University College London (UCL) (United Kingdom), who have analyzed genetic and health data from 7,146 men and women with an average age of 65 years who had participated in the English Longitudinal Study on the Aging (ELSA), a nationally representative population study in England.
The results have been published in Translational Psychiatry and revealed that people with a greater genetic predisposition to short sleep (less than five hours on a given night) were more likely to develop depressive symptoms for between four and 12 years, but that people with a greater genetic predisposition to depression did not have a greater genetic predisposition to short sleep (less than five hours on a given night).
“Using genetic susceptibility to disease, we determined that sleep likely precedes depressive symptoms, and not the other way around.”
“We have this chicken-or-egg scenario between suboptimal sleep duration and depression, they often coexist, but which comes first is largely unresolved. Using genetic susceptibility to disease, we determined that sleep probably precedes depressive symptoms, and not the other way around,” said Odessa S. Hamilton (UCL Institute of Epidemiology and Healthcare), first author of the work.
Another lead author, Dr Olesya Ajnakina, from the UCL Institute of Epidemiology and Healthcare and the Institute of Psychiatry, Psychology and Neuroscience at King’s College London, said: “Short and long sleep durations, along with depression are highly heritable and contribute significantly to the public health burden. “Polygenic scores, indices of an individual’s genetic propensity for a trait, are thought to be key to beginning to understand the nature of sleep duration and depressive symptoms.”
Interactions between genetics, sleep and depression
The researchers assessed how much genetic predisposition influenced participants using findings from previous genome-wide association studies that have identified thousands of genetic variants linked to a higher likelihood of developing depression and short or long sleep. They also analyzed non-genetic associations between depressive symptoms and sleep duration.
Overall, participants slept an average of seven hours per night. More than 10% slept less than five hours per night at the beginning of the study period, increasing to more than 15% by the end of the study period, and the proportion of participants classified as having depressive symptoms increased by 3 percentage points, from 8.75 at 11.47%.
After taking into account a variety of factors that could influence the results, such as education, economic level, physical activity, smoking and problems associated with long-term illnesses, they found that people who slept five hours or less had 2.5 times more likely to develop depressive symptoms, while people with depressive symptoms were a third more likely to experience poor sleep.
They also found a link between sleeping too much and developing depressive symptoms: Participants who slept more than nine hours were 1.5 times more likely to develop depressive symptoms than those who slept an average of seven hours. However, depressive symptoms were not associated with longer sleep four to 12 years later, which corresponded to the genetic findings.
“Suboptimal sleep and depression increase with age, and with the global phenomenon of population aging there is a growing need to better understand the mechanism connecting depression and sleep deprivation. “This study lays an important foundation for future research into the interaction of genetics, sleep and depressive symptoms,” concludes Professor Andrew Steptoe, Head of Behavioral and Health Sciences at the UCL Institute of Epidemiology and Healthcare.
