A genetic study of adult twins and a community-based study of adolescents both report novel links between sleep duration and depression.
A study of 1,788 adult twins, published in the Feb.1 issue of the journal Sleep, is described as 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 of depressive symptoms.
Among twins with a normal sleep duration of seven to 8.9 hours per night, the total heritability of depressive symptoms was 27%. However, the genetic influence on depressive symptoms increased to 53% among twins with a short sleep duration of five hours per night and 49% among those who reported sleeping 10 hours per night.
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, principal investigator Nathaniel Watson, MD, MSc, associate professor of neurology and co-director of the University of Washington Medicine Sleep Center in Seattle, said in a news release.
Both short and excessively long sleep durations appear to activate genes related to depressive symptoms, added Watson, who also serves on the board of directors of the American Academy of Sleep Medicine.
According to Watson, the study suggests that optimizing sleep may be one way to maximize the effectiveness of treatments for depression such as psychotherapy.
Study abstract: www.journalsleep.org/ViewAbstract.aspx?pid=29319
Another study, published in the same journal issue, of 4,175 individuals ages 11 to 17 is described as the first to document reciprocal effects for major depression and short sleep duration among adolescents using prospective data. Results suggest sleeping six hours or less per night increases the risk of major depression, which in turn increases the risk of decreased sleep among adolescents.
These results are important because they suggest that sleep deprivation may be a precursor for major depression in adolescents, occurring before other symptoms of major depression and additional mood disorders, principal investigator Robert E. Roberts, PhD, professor of behavioral sciences in the School of Public Health at the University of Texas Health Science Center in Houston, said in the news release.
Questions on sleep disturbance and hours of sleep should be part of the medical history of adolescents to ascertain risk.
The CDC reports that about 9% of adults in the U.S. meet the criteria for current depression, according to the news release, including 4% with major depression. The National Institute of Mental Health reports that depressive disorders have affected approximately 11% of U.S. teens at some point during their lives, and 3% have experienced a seriously debilitating depressive disorder.
Study abstract: www.journalsleep.org/ViewAbstract.aspx?pid=29307
Sleep is the official publication of the Associated Professional Sleep Societies, LLC, a joint venture of the American Academy of Sleep Medicine and the Sleep Research Society.