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.
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.
Outlook gets darker
However, Dr 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 online January 10th in Paediatrics, Dr 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% of the teens with the highest level of optimism did have at least mild depression, as indicated by their answers on a standard questionnaire. That compared with 59% of boys and 76% 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, Dr 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.
"My hunch is the optimists are a group where the threshold for experiencing depressive symptoms is a lot higher than those who have low levels," Dr Patton said.
Less vulnerable to depression
That is, they may be less vulnerable to becoming depressed in response to the more ordinary setbacks of life.
This doesn't mean telling teens to "look on the sunny side of life" will keep them from developing emotional problems, Dr Patton said.
But as teenagers go through their ups and downs, it is important to help them keep it all in perspective. Patton suggested that when kids have something go wrong in their lives, parents try to get them to have an "honest and realistic dialogue" about it.
Not everyone is sold on the power of positive thinking. A researcher not involved in the study expressed doubts about the significance of the findings.
Kids' dispositional optimism
For one, much of what the study captured may not have been kids' dispositional optimism, but their mood at the time, according to Dr James C. Coyne, who directs the behavioural oncology program at the University of Pennsylvania School of Medicine in Philadelphia.
It's not surprising, Dr Coyne told, that kids deemed very low in optimism would frequently have depression symptoms.
And even if optimism itself is protective, it probably is not all that "changeable," he said.
Optimism, he added, can be seen as a product of a person's basic personality and current circumstances - rich people typically have more reason for a bright outlook than poor people, for instance.
People revert back to who they are
But even when that poor person wins the lottery, the positive feelings eventually fade. "People revert back to who they are," Dr Coyne said.
A number of studies of adults have linked optimism to physical health benefits, like a lower risk of heart disease. But Dr Coyne said that those associations are modest, and seem largely connected to optimists' often healthier lifestyles.
He also noted that optimism research runs the risk of putting undue blame on people who are sick. Cancer patients, for instance, often feel pressured to stay positive and show a "fighting spirit," even if that goes against their true feelings.
"I think we need to adopt the attitude that when people get sick, that doesn't mean it's a personal failure," Dr Coyne said.(Reuters Health/ January 2011)