Police officers take part in a candlelight vigil at Dallas City Hall on July 11, after five of their own were killed during a shooting in the Texas city. (Tony Gutierrez/AP)

“It’s coming to the point where no lives matter.”

That was the heartbreaking statement of Joycelyn Jackson, the sister of one of the three police officers who were shot and killed by a gunman in Baton Rouge on Sunday morning. News of that tragedy came as the country was still reeling from the killings of black men by police and five police officers in Dallas by a lone gunman. And in less than two months, at least 84 people died in an attack on Bastille Day in Nice, France, and 49 were killed in the shooting at the Pulse nightclub in Orlando.

It seems as if it has been a summer of tragedy and violence. Of course, those who are suffering most are the people who are involved in these violent events — those who have lost family and friends in terrorist attacks and shootings. But psychological research suggests that people reading and watching these heartbreaking news stories can bear a burden, even if they are not directly involved. Perhaps you’ve felt it, too.

Twenty-four-hour news coverage of violent events can leave people feeling drained and hopeless. It can exacerbate symptoms of stress, anxiety and depression, research has shown. Some studies even show that news coverage of highly traumatic events can echo the post-traumatic stress felt by those actually exposed to the attack.

In a 2002 study, researchers surveyed Americans living outside New York City and found that 17 percent reported symptoms of post-traumatic stress two months after the Sept. 11, 2001, attack — suggesting that the psychological effects of a major national trauma are not limited to those who experience it directly.

Other research has demonstrated that just viewing violent imagery on social media can have similar effects. In a study last year, British researchers found that nearly a quarter of those they surveyed had some symptoms of trauma after viewing violent news events, such as school shootings or suicide bombings, on social media or online.

Studies of the effects of other natural disasters on communities have returned similar results — that those most psychologically affected are the people involved but that the effects of violence ripple outward to friends, relatives and sympathetic onlookers. And the effects do not just apply to thinking about the traumatic event: A 2011 study showed that watching negative news not only made people anxious about the world but also exacerbated their own personal, unrelated worries.

Researchers have known for a long time that nurses, counselors and other workers can experience something called “vicarious” or “insidious” trauma — when they absorb the details of their patients’ stories to such an extent that they display evidence of trauma themselves.

This stems from the biological processes that make us feel for other humans. Research shows that humans (and other animals) have something called “mirror neurons” — a special class of brain cells that fire when we see someone do something and when we do that thing ourselves.

Neuroscientists argue that this helps humans and other animals learn through imitation and that it also gives them the capacity for empathy. In fact, when we watch someone perform an action — including committing or being subject to acts of violence — our neurons fire in such a way as if we were taking part ourselves. This process can happen whether we watch an incident in person or through the media — and even when we read a book.

There are other tricks of the brain that may leave people particularly susceptible to secondhand violence, says Mary McNaughton-Cassill, a professor at the University of Texas at San Antonio who studies the connection between media consumption and stress. Our brains are far more wired to empathize with the experiences of individual people — as these stories of shooting and terrorism are often told — rather than big numbers or abstract ideas.

People are also far more scared of unpredictable and familiar events in which they feel as if they do not have control, McNaughton-Cassill says, citing seminal research by psychologist Paul Slovic. You are more likely to die by falling in a pool or crashing a car, but people in these familiar situations just feel as if they are more in control.

“The vast majority of us are never going to be near a terrorist attack or a shooting. We’re vastly more likely to be in a car crash. But because of how our brains work, we home in,” she says.

McNaughton-Cassill says that she does not think viewing shootings or terrorist attacks from afar will give someone clinical depression. But seeing them can amplify existing issues with depression, stress and anxiety, and they can affect people’s moods and outlook about the world. She cites something that psychologists call the “diathesis-stress model,” which contends that people need both a preexisting vulnerability and an external stress to get certain kinds of psychological disorders.

“Someone who is functioning well and has a satisfying life is not going to be affected by violent media. But someone who is already having problems might be,” she says.

But people today are living in an environment much more saturated by media and information than ever before. The shift to 24-hour news coverage in the past few decades and the media’s drive to capture more audience attention by featuring emotional and shocking stories has created an environment in which violent and disturbing events are far more amplified than in the past.

“You could honestly say we are all living in the biggest experiment in history,” says McNaughton-Cassill. “So we don’t really know.”

So what should you do about it? “We don’t want to become fatigued and just say, ‘Oh, well.’ But it’s overwhelming for one person to absorb all the bad things everywhere in the world,” McNaughton-Cassill says.

First, she counsels that the viewing public needs to be a lot more critical in its thinking about violent events. It’s good to be aware of crimes and injustices, but you should also recognize that terrorist attacks and mass shootings are isolated events that few people will ever be involved in.

In fact, people today are living in one of the most peaceful periods in history, with a higher quality of life around the world than ever before, and with crime in the United States near a historical low.

The American Psychological Association’s guidelines for managing the traumatic stress of terrorism echo this approach. “Let children know that institutions of democracy are still in place and our government is intact. (It can also be helpful for adults to realize this.),” the APA says.

McNaughton-Cassill also cautions people to figure out the personal level of negative news that they can be exposed to, to try to understand whether radio, TV or print journalism affects them the most, and to “turn off the news off sometimes. The first half-hour of watching the news is informative. The next four hours they’re rehashing what you saw,” she said.

Finally, she says many people less powerless when they stop just watching the news and make an effort in their communities to help. She points to the huge crowds who turned out to give blood after the Orlando attacks or who donated money after Hurricane Katrina. “Go do something local,” she says.

See also: 

Why violence is so contagious

When should a shooting really be called ‘terrorism’?

This doctor says violence is contagious, and we should treat it like a disease