You're decking the halls, wrapping presents, baking cookies and you still have a billion other things on your seasonal to-do list. No wonder you're super-stressed and hardly in the mood for anything jolly.

A new study suggests a surprising cure for easing your skyrocketing stress levels: Add one more thing to your overflowing plate. If that sounds counterintuitive, hang on a second. To feel less frazzled, you need to be utterly selfless. Take some time to help someone else.

For the study, researchers at the University of California, Los Angeles and Yale University School of Medicine, sent more than six dozen adults daily questionnaires for two weeks asking them to rate their mental health for that day and to report any positive or negative emotions they experienced. Then they were asked to also report any "prosocial" or helping behaviors they took part in. That could be anything from holding a door for someone to helping with schoolwork, reports Business Insider.

The results showed that helping others seemed to protect against the negative effects of stress.

On days when study participants were more helpful than usual, they showed no drop in the quality of their mental health or positive emotions. However, when they were less helpful than usual, they experienced higher negative emotions in response to stress and lower mental health overall.

The researchers wrote: "Results suggest that even brief periods of supporting or helping others might help to mitigate the negative emotional effects of daily stress."

Need some ideas? Here are 20 selfless things to do this holiday season. From volunteering and writing letters to giving blood and visiting a nursing home, there's sure to be something on this list that will lift your spirits.

What about cash?

There may be an even easier way to feel better during this season of over-the-top commitments and non-stop errands. Open your wallet.

Researchers at the University of British Columbia conducted an experiment to see if spending money could help lower blood pressure. Researchers gave 18 adults (ages 65 to 85) $40 a week for three weeks. Half were told to spend the money on themselves all in one day, while the other group of participants were told to spend the cash on others. Study members had their blood pressure monitored before, during and after they spent the money.

Participants who had high blood pressure saw a significant drop when they spent the cash on other people, but they experienced no change when they spent the money on themselves. People who didn't have high blood pressure likewise experienced no change.

Researchers also found that people seemed to benefit most when they were spending money on those they felt closest to.

"Although more research is needed to replicate these results, our initial findings provide some of the strongest evidence to date that daily decisions related to engaging in financial generosity can have causal benefits for physical health," wrote Ph.D. student Ashley Whillans, one of the authors of the study.

"Stepping toward better health (and happiness) may be as simple as spending your next $20 generously."

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.