A new study by researchers in Brazil finds that “night owls” have a gloomier disposition than “early birds.”
The scientists chose to study people’s sleeping schedules because depression has been shown to have a deleterious effect on sleep, said Dr. Maria Paz Loayza Hidalgo of the Universidade Federal do Rio Grade do Sul, the study’s lead author.
Indeed, research has shown that some depressed people can be aided by light therapy, in which patients sit in front of a bright light for two hours first thing in the morning in an attempt to reset sleep schedules that have been altered by depression.
In the current study, researchers randomly selected 200 healthy people with no history of mental illness and queried them about their depression symptoms and sleeping habits.
The scientists found that night owls were nearly three times as likely as early birds to have symptoms of severe depression. More remarkable yet was the fact that when compared with those who went to bed at an intermediate time, night owls were five times more likely to have severe symptoms of depression.
On average, the differences between bedtimes were small, with night owls turning in around midnight and early birds around 11 p.m. The same held true with waking time, with night owls rising on average 40 minutes later than early birds. In both groups, the total sleep duration was about the same.
“The study shows that even relatively subtle shifts in patterns of sleep seem to make a big difference in how people rate their mood,” said Dr. Ian A. Cook, an associate psychiatry professor at UCLA and director of the university’s Depression Research & Clinic program.
“That’s very intriguing stuff. Like any good study, it raises many more questions than it answers,” he told MSNBC news.
However, what is not yet known is whether the sleep schedule is causing the depression symptoms or whether those symptoms are keeping people up late, he added.
Nevertheless, the study suggests that it might be possible to enhance one’s mood with schedule changes, he said.
For those who wish to test this theory, Cook suggests using a second alarm clock set for a targeted bed time as a reminder to turn in on time.
Dr. Alan Manevitz, a psychiatrist at New York-Presbyterian Hospital/Weill Cornell Medical Center, advises steering clear of any stimulating activities close to your new bedtime. In particular, Manevitz suggests foregoing late night email checks to avoid any anxiety that might come from reading distressing messages. Also, the light from a computer screen tends to wake some people up a bit.
However, other experts believe that sleep schedules and the tendency towards depression might not be so easy to change.
Scientists have identified genes that cause some people to have a tendency to rise early and others to sleep late, said Dr. Eric Nofzinger, director of the sleep neuroimaging research program at the University of Pittsburgh School of Medicine.
There may be some natural differences in brain wiring that keep night owls more awake during the evening hours and that make them more depression prone, Nofzinger told MSNBC.
Nofzinger used a PET scanner to examine the brains of depressed patients, and found they functioned differently during sleep than those of others. In particular, depressed patients showed much more activity in parts of the brain involved in processing and experiencing emotions, he explained. As a result, they never get a full, restorative night’s sleep.
Although some people may simply have genes that make it more difficult for them to go to sleep earlier, others may simply be responding to the demands and options of modern life, said Cook.
“This study raises the question of what happens in a world of 24-hour news cycles that tempt people to stay up late,” Cook said.
“That could create a tendency to drift into the night owl pattern which could create a risk for developing mood problems.”
The study was published in the journal Psychiatry and Clinical Neurosciences.
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