The observation that most teenagers (roughly 80%, according to the National Sleep Foundation's 2006 "Sleep in America" survey) get fewer than the recommended 9 hours of sleep a night is not new. Nor, for that matter, is the connection between insufficient sleep and mood disorders, which has been borne out in sleep deprivation experiments in adults as well as in population studies in adults and teens. Everyone needs to sleep, and despite not always wanting to tuck in and call it a day, teenagers are no different than anyone else in that respect, and suffer a whole host of negative consequences when they do not get enough sleep.
A new study published in the January 2010 issue of SLEEP* looking at the effect of bedtimes set by parents on mood in 15,659 7-12th graders found that the later a child's bedtime was set, the more likely the child was to have symptoms of depression and/or thoughts about suicide. Later bedtimes were also found to correlate with shorter sleep duration (not a big surprise) and a sense of not getting enough sleep, both as reported by the child. Those children with earlier bedtimes were also more likely to describe their parents as caring more about them than those with later bedtimes. Overall, children whose bedtime was set at midnight or later were 24% more likely to suffer from depression, and 20% more likely to have suicidal thoughts than children whose bedtimes were 10 PM or earlier.
As with all studies of this type, questions of cause and effect arise: did the later bedtimes truly cause the increased depression, or did underlying depression lead to later bedtimes? Sleep disturbances are one of the defining characteristics of depression. It may be that in many instances, pre-existing depression influenced the hour at which bedtimes were set. Lax limit setting on the part of parents, manifesting as unfettered bedtimes, could also have contributed to a sense in some that their parents didn't care as much about them as they felt they should, which in turn may have led to symptoms of depression.
Still, the findings are intriguing, and worth paying attention to. Despite many and frequent protests to the contrary, teenagers really do need a certain amount of sleep (about 9 hours/night). It is very important to realize that sleep is not something to be done when there is nothing better, or more exciting, left to do. Sleep is necessary for both good short term function and long term physical and mental health. Setting age appropriate bedtimes, while not always easy to enforce, is, ultimately, not all that different from setting limits on other activities which can adversely affect health, such as cigarette smoking. As the findings of this study suggest, it is likely to be well worth the effort.
Dennis Rosen, M.D.
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*Gangswisch et al. Earlier parental set bedtimes as a protective factor against depression and suicidal ideation. Sleep 2010;33(1):97-106.