A genetic study of adult twins and a community-based study of adolescents have reported novel links between sleep duration and depression. Both short and excessively long sleep durations appear to activate genes related to depressive symptoms.

"We were surprised that the heritability of depressive symptoms in twins with very short sleep was nearly twice the heritability in twins sleeping normal amounts of time," said Nathaniel Watson, associate professor of neurology and co-director of the University of Washington Medicine Sleep Centre in Seattle.

This new research emphasizes that we can make an investment in our health by prioritizing sleep, added M Safwan Badr, president, American Academy of Sleep Medicine.
A study of 1,788 adult twins is the first to demonstrate a gene by environment interaction between self-reported habitual sleep duration and depressive symptoms. Results suggest that sleep durations outside the normal range increase the genetic risk for depressive symptoms.

Among twins with normal sleep duration of seven to 8.9 hours per night, the total heritability of depressive symptoms was 27 percent. However, the genetic influence on depressive symptoms increased to 53 percent among twins with a short sleep duration of five hours per night and 49 percent among those who reported sleeping 10 hours per night.

Another study of 4,175 individuals between age 11 and 17 is the first to document reciprocal effects for major depression and short sleep duration among adolescents using prospective data. Sleeping six hours or less per night increases the risk for major depression, which, in turn, increases the risk for decreased sleep among adolescents, said the study.

Optimizing sleep may be one way to maximize the effectiveness of treatments for depression such as psychotherapy."Healthy sleep is a necessity for physical, mental and emotional well-being," said Badr.

Robert E Roberts, professor of behavioural sciences at University of Texas, said ‘sleep disturbance and hours of sleep should be part of the medical history of adolescents to ascertain risk’.


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