Getting too little sleep might be a sign of - or even a contributor to - emotional problems, anxiety and suicidal thoughts among teens, according to a large study from Europe.

Based on data about the sleep habits of nearly 12,000 teens across 11 European countries, researchers found that a student with suicidal thoughts could be predicted to sleep about 36 minutes less each night compared to counterparts with no suicidal thoughts. For teens with severe emotional problems, the amount of sleep lost would be about 30 minutes, on average, each night.

"This is not a very large effect," study author Laura Mandelli told Reuters Health in an email. Mandelli is assistant professor of psychiatry at the University of Bologna in Italy.

And the researchers cannot say whether there is a cause-and-effect relationship between the sleep patterns and mental health problems seen in the study.

Lack of sleep among teens has been linked in other research to many negative health effects, including high blood pressure. And researchers have found that teens are generally going to bed later.

Past research has also shown that teens need between eight and a half and nine hours of sleep each night. Teens in the current study averaged about eight hours of sleep.

Mandelli and her colleagues asked them about total hours slept during school nights, or Monday through Friday. Teens also answered questions about whether they worried a lot or spent long periods alone.

"The data collection is impressive - and that is very difficult to get for studies like this," said Kwang-Sig Lee of Yonsei University College of Medicine in Seoul, who was not involved in the study.

"This study confirms previous findings, but there is basically nothing new here," Lee told Reuters Health.

"It is important to realize that the 11 countries have different climates and different socio-cultural conditions, which makes it somewhat difficult to generalize the results," he added.

In the study, French teens reported the lowest average sleep times and Irish teens reported the highest. Teens in Israel reported the widest range of sleep times, from less than six hours to about nine-and-a-half.

The authors write in the journal Sleep Medicine that self-reports, like those in this study, can be inaccurate because of faulty recall, or the desire to "please or displease, or provoke, particularly in adolescents."

"It's important to look at how to increase hours of sleep among teenagers," said Dr. Iris F. Litt, director of the Center for Advanced Study in the Behavioral Sciences at Stanford University in California.

But because of the study's design, "you cannot say what is causing the sleep loss," she said.

Litt is a pioneer researcher in the field of adolescent medicine. She was not involved in the current research.

"I would be much more concerned with knowing why the kids aren't sleeping," Litt told Reuters Health.

"So I'd be worrying about bullying or sexual abuse - what is causing them to be depressed and anxious?" she said.

Both outside experts said it's important to learn more about this subject.

"We do need more discussion on this issue of sleep deprivation among young people," Lee said. He added that young people already face additional stressors, such as low youth employment, around the world.

Regarding what to do, Lee said that parents "could focus more on emotional problems that their children may have." He added that psychological counseling might also be helpful.

"You've got to know why they are not sleeping before you can intervene and help," Litt said.