“People tend to liken their emotions to the weather, viewing them as uncontrollable,” study researcher Barbara Fredrickson, of the University of North Carolina, said in a statement. “This research shows not only that our emotions are controllable, but also that we can take the reins of our daily emotions and steer ourselves toward better physical health.”

Researchers also found that social connections are a big part of why it’s possible to “will” yourself to have more positive emotions.

It’s well known, of course, that shoe traction influences athletic performance, especially in sports that involve sprinting or cutting, meaning abrupt rapid shifts in direction. In broad terms, more traction leads to better results, but do they affect your chances of getting injured.

But the weight loss maxims found in diet books do not always hold up in the real world. So two researchers at Cornell University recently devised an experiment that put this notion to the test.

The study, published in JAMA Internal Medicine, was carried out in two phases.

There is no hard evidence linking these increases to the rising popularity of indoor tanning. But most dermatologists have no doubt.

“Dermatologists would like to ban tanning beds,” said Dr. Hooman Khorasani, a dermatologist and chief of the division of Mohs, Reconstructive & Cosmetic Surgery at the Mount Sinai School of Medicine in New York. “Tanning beds are directly related to risk.”

Fair skin significantly increases the risk of melanoma, as do sunburns, said Dr. Carlos Rodriguez-Galindo, director of the pediatric solid tumor program at the Dana-Farber/Boston Children’s Cancer and Blood Disorders Center, and coauthor of the study in Pediatrics.

The unusual message was contained in a scientific statement published on Thursday by the American Heart Association, which convened a panel of experts to review years of data on the cardiovascular benefits of owning a pet. The group concluded that owning a dog, in particular, was “probably associated” with a reduced risk of heart disease.

People who own dogs certainly have more reason to get outside and take walks, and studies show that most owners form such close bonds with their pets that being in their presence blunts the owners’ reactions to stress and lowers their heart rate, said Dr. Glenn N. Levine, the head of the committee that wrote the statement.

The research, published in the Journal of Personality, shows that optimism’s benefits are seen in both high- and low-income countries, suggesting it’s not “just a luxury that exists in wealthy, industrialized nations,” study researcher Shane Lopez, of the University of Kansas, said in a statement.