Washington DC [US], October 22
According to a new genetic study headed by UCL (University College London) experts, sleeping less than five hours per night may increase the risk of getting depressive symptoms.
Historically, poor sleep has been seen as a side effect of mental ill health, but this study found that the link between sleep and mental illness is more complex.
The study, published in the journal Translational Psychiatry, analysed data from people with an average age of 65 and found short sleep was associated with the onset of depressive symptoms.
Lead author Odessa S. Hamilton (UCL Institute of Epidemiology & Health Care) said: “We have this chicken or egg scenario between suboptimal sleep duration and depression, they frequently cooccur, but which comes first is largely unresolved. Using genetic susceptibility to disease we determined that sleep likely precedes depressive symptoms, rather than the inverse.”
For the study, the researchers used genetic and health data from 7,146 people recruited by the English Longitudinal Study of Ageing (ELSA), a nationally representative population study in England.
They found that 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 4-12 years, but that people with a greater genetic predisposition to depression did not have an increased likelihood of short sleep.
Senior author Dr Olesya Ajnakina (UCL Institute of Epidemiology & Health Care and the Institute of Psychiatry, Psychology & Neuroscience at King’s College London) said: “Short and long sleep durations, along with depression, are major contributors to 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.”