From Medscape Medical News
January 1, 2010 — Adolescents whose parents mandate bedtimes of midnight or later are 24% more likely to be depressed and 20% more likely to express suicidal ideation than adolescents whose parents set bedtimes of 10 pm or earlier, according to a study in the January 1 issue of Sleep.
These findings suggest that earlier parentally set bedtimes may help protect adolescents from depression by ensuring they get enough sleep. James Gangwisch, PhD, Columbia University Medical Center, New York City, and multicenter colleagues found that the average amount of sleep reported by 15,659 adolescents involved in the National Longitudinal Study of Adolescent Health (Add Health) was 7 hours and 53 minutes — considerably less than the 9 or more hours recommended for adolescents by the American Academy of Sleep Medicine.
However, adolescents whose parents had set a bedtime of 10 pm or earlier slept 33 minutes more, on average, than those with a bedtime of 11 pm, and 40 minutes more on average than adolescents with a parental bedtime of midnight or later. Adolescents who reported getting on average 5 or fewer hours of sleep per night were also 71% more likely to be depressed and 48% more likely to think about committing suicide than adolescents who reported getting 8 hours of sleep a night.
"Short sleep duration could be either a symptom of depression or it could be causative of depression, so we tried to get at this question by looking at parentally mandated bedtimes because if you leave it up to a child as to when they go to bed, an argument could be made that [lack of] sleep is simply a symptom of depression," Dr. Gangwisch told Medscape Neurology. "And our study lends support to the idea that lack of sleep could be causative for depression."
Add Health involved a nationally representative sample of adolescents in the United States who were in grades 7 to 12 between 1994 and 1996. An 18-item version of the Centers for Epidemiologic Study–Depression Scale was administered to assess individuals for the presence of depressive symptoms, and the presence of suicidal ideation was determined by responses to the question: "During the past 12 months, did you ever seriously think about committing suicide?"
As investigators note, more than two thirds of Add Health participants reported going to bed at a time that complied with their parents' reported set bedtime. In unadjusted analyses, adolescents with late parentally mandated bedtimes of midnight and later were 42% more likely to be depressed, and those with set bedtimes of 11 pm were 15% more like to be depressed, than adolescents with set bedtimes of 10 pm.
Again in unadjusted analyses, adolescents with parentally set bedtimes of midnight or later and 11 pm were 30% and 15% more likely to suffer from suicidal ideation, respectively, in comparison with adolescents with parental set bedtimes of 10 pm. Risks were attenuated depending on the model used.
"Adolescents want to go to bed later now because there are so many different distractions, plus they have to get up really early for school, so it's easy for them not to get enough sleep," Dr. Gangwisch noted.
"But what we are saying is that getting adequate sleep is very important for mental health, and compromising on the amount of sleep by doing other activities can have negative consequences, including a increased risk of depression."Substantiated Empirical Belief
Commenting on the study, William Kohler, MD, from the Florida Sleep Institute, Springhill, told Medscape Neurology that the study "substantiated the empirical belief that lack of sleep leads to difficulties with cognition." Even though inherent inaccuracies do occur with a questionnaire-based study such as this one, "the sample size was large, and it was a very good study." There was, as he indicated, no information on the quality of sleep reported by the adolescents, so that participants might have been in bed 8 hours but had gotten little sleep.
Still, Dr. Kohler feels that the study underscored how important it is for physicians to ask adolescent patients about their sleep habits — what time they go to bed, how much sleep they have or perceive they get — to make sure poor sleeping habits are not contributing to underlying depression.
He also feels that schools need to look at start times for students because "no matter how much money we throw at public education, if children are getting up at 5 in the morning to get to school, they are not going to learn properly because they are sleep-deprived."
Financial support for this study was provided by a grant from the Robert Wood Johnson Health and Society Scholars Program at Columbia University, but it was not an industry-supported study. Dr. Gangwisch and Dr. Kohler have disclosed no relevant financial relationships.