Studies find new links between sleep duration and depression
A genetic study of adult twins and a community-based study of adolescents both report novel links between sleep duration and depression. The studies are published in the Feb. 1 issue of the journal Sleep.
“Healthy sleep is a necessity for physical, mental and emotional well-being,” said American Academy of Sleep Medicine President Dr. M. Safwan Badr. “This new research emphasizes that we can make an investment in our health by prioritizing sleep.”
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 a 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.
“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 principal investigator Dr. Nathaniel Watson, associate professor of neurology and co-director of the University of Washington Medicine Sleep Center in Seattle, Wash.
“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.
The relationship between sleep and depressive illness is complex – depression may cause sleep problems and sleep problems may cause or contribute to depressive disorders. For some people, symptoms of depression occur before the onset of sleep problems. For others, sleep problems appear first. Sleep problems and depression may also share risk factors and biological features and the two conditions may respond to some of the same treatment strategies. Sleep problems are also associated with more severe depressive illness.
Insomnia is very common among depressed patients. Evidence suggests that people with insomnia have a ten-fold risk of developing depression compared with those who sleep well. Depressed individuals may suffer from a range of insomnia symptoms, including difficulty falling asleep (sleep onset insomnia), difficulty staying asleep (sleep maintenance insomnia), unrefreshing sleep, and daytime sleepiness. However, research suggests that the risk of developing depression is highest among people with both sleep onset and sleep maintenance insomnia.
Sleep apnea is also linked with depression. In a studyof 18,980 people in Europe conducted by Stanford researcher Maurice Ohayon, MD, PhD, people with depression were found to be five times more likely to suffer from sleep-disordered breathing (sleep apnea is the most common form of sleep disordered breathing). The good news is that treating sleep apnea with continuous positive airway pressure (CPAP) may improve depression; a 2007 studyof OSA patients who used CPAP for one year showed that improvements in symptoms of depression were significant and lasting.
In many cases, because symptoms of depression overlap with symptoms of sleep disorders, there is a risk of misdiagnosis. For example, depressed mood can be a sign of insomnia, sleep apnea or narcolepsy. Restless legs syndrome (RLS), a neurological condition that causes discomfort in the legs and sleep problems, is also associated with depression. According to the Restless Legs Syndrome Foundation, approximately 40% of people with RLS complain of symptoms that would indicate depression if assessed without consideration of a sleep disorder.
Another study of 4,175 individuals between 11 and 17 years of age is 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 for major depression, which in turn increases the risk for 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,” said principal investigator Dr. Robert E. Roberts, professor of behavioral sciences in the School of Public Health at the University of Texas Health Science Center in Houston, Texas. “Questions on sleep disturbance and hours of sleep should be part of the medical history of adolescents to ascertain risk.”
Getting six to nine hours of sleep per night is associated with higher ratings for quality of life and lower ratings for depression, suggests a research abstract that will be presented Tuesday, June 14, in Minneapolis, Minn., at SLEEP 2011, the 25th Anniversary Meeting of the Associated Professional Sleep Societies LLC (APSS).
Results show that people with a “normal” sleep duration of six to nine hours per night had higher self-reported scores for quality of life and lower scores for depression severity compared to short and long sleepers. These differences were statistically significant in all comparisons. Among patients who reported having perfect health, there were a higher percentage of normal sleepers, who also had significantly lower scores for depression severity compared to short and long sleepers with perfect health.
“These results are important because they provide more information about the importance of getting enough sleep, which is usually six to nine hours per night,” said principal investigator Dr. Charles Bae, neurologist at the Cleveland Clinic Sleep Disorders Center in Ohio. “People may already expect that their quality of life could be decreased when they do not get enough sleep, but they may not realize that sleeping too much can also have a negative impact.”
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Source: American Academy of Sleep Medicine
The Centers for Disease Control and Prevention reports that about nine percent of adults in the U.S. meet the criteria for current depression, including four percent with major depression. The National Institute of Mental Health reports that depressive disorders have affected approximately 11 percent of U.S. teens at some point during their lives, and three percent have experienced a seriously debilitating depressive disorder.
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The monthly, peer-reviewed, scientific journal Sleep is published online by the Associated Professional Sleep Societies LLC, a joint venture of the American Academy of Sleep Medicine and the Sleep Research Society. The AASM is a professional membership society that improves sleep health and promotes high quality patient centered care through advocacy, education, strategic research, and practice standards.
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Lynn Celmer
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American Academy of Sleep Medicine