Parents, take note: Enforcing an earlier bedtime for your unruly teenager may be more than worth it. In the Jan. 1 issue of Sleep, researchers at Columbia University demonstrate a strong correlation between lack of sleep and depressive symptoms in adolescents. The study examined more than 15,000 adolescents and their parents.
For many experts on depression, the result is no surprise. Researchers have long known that there is a strong relationship between sleep and the disease, although the nature of that link has remained elusive.
“Sleep is actually one of the diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders for depression,” says Jane Gaultney, a psychologist at the University of North Carolina, Charlotte, who studies sleep and cognition. “One of the things clinicians look for is too much or too little sleep. We know there’s a strong connection.”
But because sleeping problems are a classic symptom of the disease, the potential role they play in the development of depression or depressive symptoms has been hard to pin down. James Gangwisch, a sleep epidemiologist at Columbia University and lead author on the Sleep study, says it supports the idea there is a bi-directional relationship between sleep and mood.
Cause or effect?
“Our idea is that lack of sleep is not just a symptom of depression,” Gangwisch says. “It can either cause or exacerbate it. It’s certain an intuitive idea—when we don’t get enough sleep, we feel tired, lethargic, irritable and lose motivation to do the things we need to do, all things associated with depression as well.”
Gangwisch and colleagues looked at bedtimes set by parents for adolescents as well as the times the adolescents reported they actually went to bed, then correlated it with reports of depressive symptoms.
“Lack of sleep is a symptom of depression, so if an adolescent is depressed, it can affect when they go to bed at night and how much sleep they get,” he says. “But what should not be affected is the parent-set bedtime.”
The group found that when parents set earlier bedtimes for their teens, the teens more reported more sleep and were less likely to suffer from depression or depressive symptoms. Gangwisch admits that this does not prove a causal relationship between lack of sleep and depression. But the study replicates other findings that sleep plays an important role in mood.
“What else we see here is the importance of parents working with adolescents to set reasonable bedtimes for them,” he says. “Whether parents think so or not, setting earlier bedtimes helps and seems to have a protective effect.”
Establishing more than a correlation
Over the past few decades, several studies have shown this strong correlation between sleep and mood disturbance—both in adults and adolescents. But how can researchers bridge the gap and determine if one causes the other? It’s not an easy task, but many scientists are now hard at work on exactly that problem. William Killgore, a researcher at Harvard Medical School, says a closer look at what happens in the brain after sleep deprivation can help.
“There’s a theory that sleep deprivation leads to a decrease of metabolic activity in the prefrontal cortex, the area involved in controlling behavior and emotion,” he says. “It may be that if you go for a long period of time without good sleep, these emotional centers start running wild—the person gets more depressed and sleeps less and gets more depressed. It’s a bit of a vicious cycle.”
Francesco Benedetti, an expert in chronotherapy at the Vita-Salute San Raffaele University in Milan, agrees that a closer look at the brain is needed to understand the true nature of the relationship between sleep and mood—and hopes that it will be a focus in future sleep research.
“Early studies show that pediatric patients experience profound changes in sleep patterns before the onset of a first depressive episode, but we don’t yet know what is happening in the brain itself,” he says. “If we can observe and document the changes that occur in the brain, we may be able to prevent the onset of depression.”
But in the meantime, Gangwisch says there is one piece of actionable advice from his study: Parents need to get serious about bedtimes. “I know parents throw up their hands and say ‘I can’t control my teen!’ But I think parents really can influence what time their kids go to bed at night and help ensure they get enough sleep.”