Sleeping less than five hours a night increases the risk of depression

Sleep Consistently less than five hours a night could increase the risk of developing depressive symptoms, according to a genetic study led by researchers at University College London (UCL).

The results are published in the journal Translational Psychiatry and the study analyzed data from people with an average age of 65 years: little sleep is associated with the appearance of depressive symptoms.

Poor sleep has historically been considered a side effect of poor mental health, but this research found that the link between sleep and mental illness is more complex, says a UCL statement.

“We have this chicken or egg scenario between suboptimal sleep duration and depression (…). Using genetic susceptibility to the disease, we determined that sleep is likely to precede depressive symptoms, rather than the other way around.”says Odessa S. Hamilton, author of the work.

The researchers used genetic and health data from 7,146 people recruited into the ELSA Longitudinal Study of Aging, a nationally representative population-based report in England.

The team assessed the strength of genetic predisposition among participants, using results 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 duration.

They found that people with a greater genetic predisposition to sleep little (less than five hours a night) were more likely to develop depressive symptoms within 4-12 years.

However, people with a greater genetic predisposition to depression were not more likely to have poor sleep.

In the words of Olesya Ajnakina, also from UCL, “Short and long sleep duration, along with depression, are factors that contribute greatly to the public health burden and are highly heritable.”

“Polygenic scores, indices of an individual’s genetic propensity for a trait, are considered key to beginning to understand the nature of sleep duration and depressive symptoms.”.

For Andrew Steptoe, “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.”

“This study lays an important foundation for future research into the intersection of genetics, sleep, and depressive symptoms.””.

On the other hand, and in another non-genetic analysis, the researchers also revealed a link between sleeping a lot 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.