A good mood really is contagious, even on social media. According to a new study, the mood of your Facebook updates is directly influenced by the moods of those in your newsfeed. The study, which was conducted by researchers at the University of California, Yale, and Facebook, examined statuses on the popular social network with a particularly positive or negative emotional bent, as identified by algorithm.

The study, which was conducted by researchers at the University of California, Yale, and Facebook, examined statuses on the popular social network with a particularly positive or negative emotional bent, as identified by algorithm. The researchers first proved that rainy days caused fewer positive statuses and more negative ones—even when the program eliminated statuses explicitly about the weather. During a rainy day, they found, a city’s number of negative posts will increase by 1.16%, and positive ones will decrease by %1.19.

The researchers then looked at friends of the rained-in parties—but ones who lived in other cities, where the weather was fine. This group was affected by their wetter friends: For every negative post from the rainy group, dry friends posted 1.29 more negative posts than would normally be expected. Positive posts had a slightly stronger effect, inspiring 1.75 more positive posts. “Effectively this means that 1-2 people were indirectly affected,” researcher Massimo Franceschettitold Quartz.Not exactly an epidemic of goodwill, but a notable increase. “We showed,” says Franceschetti, “that social networks can actually magnify and promote social synchrony. This could mean that social networks actually make the world more volatile, because people are more prone to synchronize emotionally with peers around the world.”

Contagious emotion isn’t a new idea: “We know that emotions are contagious in a sense,” saysFranceschetti. “When you go to a restaurant and you’re greeted with a smile, this makes you feel better. It improves your experience. But isolating this network effect on such a massive scale—with the help of a huge online social network—allows us to measure the contagion more effectively.” The authors hope that knowledge of this effect will inform everything from marketing tactics to acts of good will. “The benefit of a good action can spread,” says Franceschetti. “Providing better care for the suffering could effect numerous others’ happiness as well.”

We all expect to have our opinions influenced by peers on social media, and it seems that their moods may sway us as well. If your newsfeed is full of grousers, perhaps it’s time to find new (Facebook) friends.