Watching wall-to-wall coverage of domestic terrorism can cause people to develop symptoms of post-traumatic stress disorder. Those symptoms, in turn, can cause people to seek out more upsetting coverage in the future, creating a cycle that can be hard to break.

For a study published today in the journal Science Advances, UC Irvine psychologist Rebecca Thompson and her team spent three years collecting survey data from over 4,000 US residents. The team surveyed these residents four times, asking about media consumption and mental health. The cycle began with the Boston Marathon bombings in 2013. (Previous research showed that people exposed to six hours of daily coverage of the Boston Marathon bombing in the week following the attack had more stress than those who were actually there.) Thompson and her team found that the more people saw about the bombings, the more upset they were six months later, and the more distressed they were about future negative events.

“When something bad is happening, you want to know what’s happening to be able to formulate a response to it,” explains Thompson. It’s normal to try to gather information in these circumstances, “but the problem is that when people are seeing a lot of really distressing images and sensationalized content in the media, this doesn’t necessarily make them feel better.” It makes them feel worse and leads to more worry about other terrible events happening in the future. The people who were most worried about future negative events were the ones who consumed the most media coverage of the 2016 Orlando nightclub shooting, which made them even more distressed.

Today’s study focused on those two acts of domestic terrorism, but the team is also looking into whether the same patterns hold for natural disasters, such as hurricanes. Thompson became interested in the psychological effects of natural disasters as an undergraduate in 2011 after a tornado nearly hit her campus. “Being a part of that community during such a sort of life-changing event really sparked my interest in people’s response to community traumas,” she says. Earlier this year, Thompson co-authored a study about how people who spent more time following news about Hurricane Irma experienced more negative psychological effects.

There are plenty of questions remaining, according to Thompson. For one, we don’t know yet what kind of media (for instance, television versus online) is the most harmful, or whether sounds and images together or separately is most distressing. For now, the key takeaway is that it’s good to consume media in moderation since it’s natural to feel anxious if you don’t know what’s going on. “But the kicker is that what you don’t want to be doing is being completely consumed by this coverage and spending all day refreshing Twitter and having the cable news playing with the same video thing shown over and over and over again,” Thompson says. That could have lasting effects.