More money, more stress. As incomes go up, you'd think people's happiness would, too. Not always the case. If you have a stressful job or a lot on your plate, you're probably feeling crunched for time.

The solution? Buy yourself time. Money can buy happiness if you spend it in the right way: Pay other people to do tasks that save you time. It'll ease to-do list overwhelm and you'll simply be happier. That's according to a new study published in Proceedings of the National Academy of Sciences on the subject of happiness.

"People who spent money to buy themselves time, such as by outsourcing disliked tasks, reported greater overall life satisfaction," lead author and Harvard Business School assistant professor Ashley Whillans told New York Times.

Whillans and colleagues from University of British Columbia, Maastricht University and Vrije Universiteit Amsterdam collaborated on an international experiment to answer the age-old question: Can you buy happiness? Turns out if you're buying back your own time, the answer is yes.

It's less abstract than it sounds. The researchers compared the happiness of people who spent money on time-saving services versus those who bought material things. Across the board, people who used money to free up their time reported greater life satisfaction. Furthermore, "using money to buy time can protect people from the detrimental effects of time pressure on life satisfaction," the researchers wrote.

Even if the time-saving task is one you could have easily done yourself -- such as cleaning the house, picking up groceries or doing a simple home repair -- paying someone else to do it for you gives you back your time. Your to-do list gets shorter. You no longer have to tend to a nagging task you've been dreading. So now you can spend your time in a way that actually makes you happy.

Time-saving results

The experiment began with a simple experiment. Study co-author Elizabeth Dunn explained to NPR how it all went down: They gave participants $40. One group was asked to spend the money in a way that would free up their time. People used the money to hire help with errands, grocery shopping and cleaning. The other group was directed to put their $40 towards a material purchase. One guy bought clothes. Another woman bought nice wine.

The people who spent money on the unenjoyable chores and errands had better results. By paying someone else to do mundane tasks, Dunn and her colleagues noticed a difference in their happiness.

For the second part of the study, the researchers surveyed 6,000 people in the U.S., Canada and Europe. Participants answered questions about if they spent money on time-saving tasks. They were also asked to rate their happiness and life satisfaction. In this self-reported portion of the study, people who put money towards freeing up their own time reported higher levels of happiness. ​

Logically, the results seem to make perfect sense. Time is a limited resource. If you can afford to spend the money, why not structure your day so you have more of time? But in practicality, it can be difficult to put money towards something you could just as easily have done yourself. So try re-framing it like this: You can always make more money. But you can't make more time.