It seems parents have long been right. Going to bed early is key to getting enough sleep and helping adolescents feel on top of the world, a new study reported.

A lack of sleep among youngsters may trigger depression and suicidal thoughts, according to the study by the Columbia University Medical Center.

"Our results are consistent with the theory that inadequate sleep is a risk factor for depression, working with other risk and protective factors through multiple possible causal pathways to the development of this mood disorder," said lead author James Gangwisch.

"Adequate quality sleep could therefore be a preventative measure against depression and a treatment for depression," he added in the study published in the Friday issue of Sleep magazine.

The study followed the nightly habits of some 15,659 college and high-school students, and found those who consistently went to bed after midnight had a 24 percent higher risk of depression than those who turned in before 10:00 pm.

Night owls also ran a 20 percent higher risk of battling suicidal thoughts, the study added.

The American Academy of Sleep Medicine recommends that adolescents should sleep at least nine hours or more a night. Those who were tucked in before 10:00 pm reported they slept on average about eight hours and 10 minutes.

But that amount of sleep dropped significantly for those in bed after midnight.

And adolescents who slept five hours or less a night were 71 percent more likely to suffer depression and 48 percent more at risk of becoming suicidal, the study said.

"It is a common perception and societal expectation that adolescents do not need as much sleep as pre-adolescents, yet studies suggest that adolescents may actually require more sleep," said Gangwisch.

"Studies have found that adolescents do not go to bed early enough to compensate for earlier school start times, and transitions to earlier school start times have been shown to be associated with significant sleep deprivation."

(Read by Lee Hannon. Lee Hannon is a multimedia journalist at the China Daily Web site.)

(Agencies)