The study, which followed more than 5,600 Australian teens, found that those with the most optimistic views of themselves and the world around them were less likely to develop depression symptoms over the next year. Whether their optimism deserves the credit is not clear. And the broader questions of whether optimism is something that can be "taught" -- and if it's even a good idea to try -- are up in the air.

But researchers say the findings do argue for helping teenagers to better manage their sometimes dramatic reactions to life's ups-and-downs. "We don't really know why some teens are more optimistic than others, and how teachable optimism is," said the study's lead researcher, Dr. George C. Patton of the University of Melbourne and Royal Children's Hospital in Australia.

In an e-mail he noted that people's tendency to accentuate the positive -- or not -- probably takes shape early in life, and may be related to their parents' dispositions. However, Patton also said that kids' outlook often gets darker as they go through their teen years. "So what is perhaps avoidable is the catastrophic reaction some teens can have when something goes wrong," he said.

For their study, published in the journal Pediatrics, Patton and his colleagues followed 5,634 Australian students who were between the ages of 12 and 14 at the outset.

The students completed questionnaires that gauged their tendency to have an "optimistic thinking style." One-quarter were judged to have a "very high" level of optimism: they generally saw the world and other people as good, liked themselves and felt like they had a bright future.

These positive-thinking teens were less likely to report depression symptoms at the study's start.

About 15 percent of the teens with the highest level of optimism also scored high enough on a standard questionnaire to suggest at least mild depression. That compared with 59 percent of boys and 76 percent of girls with "very low" optimism levels who showed signs of depression.

More importantly, the researchers say, the most optimistic teens were half as likely to report new depression symptoms one year later, compared with their least-positive peers. The findings do not prove that optimism itself wards off depression. And it's not clear why the relationship exists.

The researchers looked at whether the highly optimistic teens had had fewer stressful life events in the past year -- things like the death or serious illness of a family member, or a relationship break-up. That was not the case, Patton said. Nor did optimistic kids seem to react to major stressors any better; such experiences were linked to an increased risk of new depression symptoms in all teenagers, regardless of their optimism levels.