Study: Less depression, suicide thoughts for teens with earlier bedtimes

Late nights may make teenagers more prone to depression and suicidal thoughts by depriving them of sleep, according to a Columbia University study.

Teens whose parents let them go to bed past midnight were 24 percent more likely to be depressed and 20 percent more likely to have contemplated suicide than peers whose parents set bedtimes at or before 10 p.m., the researchers said last week in the journal Sleep. Earlier bedtimes may be protective because they increase the likelihood of getting enough sleep, they said.

The study is the first to show that sleep deprivation may cause depression and suicidal thoughts in adolescents. Previous research has shown a link, though the relationship wasn't clear because insomnia can be a symptom of depression.

"Our results strengthen the argument that lack of sleep can cause depression as opposed to simply being a symptom of depression," James Gangwisch, the study's lead author and an assistant professor at the university's medical center, said in an e-mail. "Adequate quality sleep could therefore be a preventive measure against depression and a treatment for depression."

About 4,400 Americans between 10 and 24 commit suicide each year, making it the third most common cause of death in the age group, according to the federal Centers for Disease Control and Prevention (CDC).

Gangwisch and colleagues studied data from 15,659 U.S. students, who were in grades seven to 12 between 1994 and 1996, and their parents. Seven percent of the teens were found to have depression and 13 percent said they seriously contemplated suicide during the preceding 12 months. The association was stronger for girls and older children, according to the study.

Teenagers whose parents said they should go to bed at 10 p.m. or earlier slept for 8 hours 10 minutes on average, 40 minutes more than those with bedtimes set at midnight or later, the researchers found. That's less than the nine or more hours of sleep for adolescents recommended by the American Academy of Sleep Medicine, a joint publisher of the journal.

Those who typically slept for five hours or less each night were 71 percent more likely to experience depression and 48 percent more likely to have thought about taking their own lives than those who got eight hours of sleep, according to the study paid for by the university.

Lack of sleep may affect brain responses to negative stimuli, hinder a person's ability to cope with stress and impair relationships with peers and adults, the researchers said. It may also affect judgment, concentration and impulse control.

Almost 70 percent of teenagers reported going to bed at the time set by their parents, and two-thirds of the rest said they usually went to bed within an hour after the limit, the study found. More than half of parents surveyed said they sent their children to bed by 10 p.m. or earlier on weeknights, and 25 percent said they allowed their kids to stay up until midnight or later.