Patti Neighmond

A majority of Americans say they're stressed at work. And it's clear the burden of stress has negative effects on health, including an increase in heart disease, liver disease and gastrointestinal problems.

If anyone can handle the stress of parenting in the teen years, you'd think it would be a high school teacher.

That's how Amy Myers felt. She teaches high school English in a suburb of Boise, Idaho, where she says she has "pseudo parented" about 3,000 teenagers "who I have talked to, given advice to, guided, directed, even lectured about teenage issues," she says.

It's well known that routine physical activity benefits both body and mind. And there are no age limits. Both children and adults can reap big benefits.

Now a study published in Clinical Psychological Science, a journal of the Association for Psychological Science, explores whether certain factors may help to explain the value of daily physical activity for adolescents' mental health.