Most people react to violent events such as last month's school shooting in Parkland, Fla., with shock, outrage, numbness, horror and revulsion.  Yet the widespread public attraction to violence has been well-documented throughout history.

In ancient Rome, crowds of 50,000 gathered to watch sport-killing in the Coliseum.  In the Middle Ages, thousands of London's executions occurred amid a fair-like atmosphere that included food vendors, ticket sales, and premium seating.

Today, first-person shooter video games such as Call of Duty continuously break sales records.  Television programs such as  Netflix's new reality show, The Push, dangle homicide as entertainment to draw viewers.  The same network's controversial drama 13 Reasons Why included a lengthy and graphic scene in which a teenager took her life in the season finale.  The Alienist, a TNT mini-series, contains disturbing images of murdered children.

As we strive to enhance our physical and emotional well-being, both individually and as a society, the pervasiveness of media violence raises important questions for our health: What increases the likelihood of seeing violent content?  How does it affect us?  Can anything be done to reduce its negative impact?

Neuroscience has begun to demystify the biological side of this equation.  Some studies indicate that viewing aggression activates regions of the brain responsible for regulating emotions, including aggression. Several studies, in fact, have linked viewing violence with an increased risk for aggression,  anger, and failing to understand the suffering of others.  Viewers are less likely to help others, feel sympathetic toward victims, and express empathy.

Though viewing violent content does not necessarily lead to aggression, people who enjoy such programs can experience activation in the same pleasure center of the brain stimulated by eating, having sex, and taking drugs.

From an evolutionary perspective, people are more likely to pay attention to emotionally charged information in order to avoid threats to survival, which may help explain why many are drawn toward violent content.

One psychological model proposes that frequent exposure to violent media helps establish aggressive "behavioral scripts" and more positive attitudes toward aggression.

Evidence suggests that watching violent media takes a toll on us physically and emotionally.

Seeing violent scenes on television can trigger a kind of mental "camera flash" in which high levels of arousal join the release of hormones associated with storing memories.  The more intense the negative feelings stirred by violent media, the more vivid and available those memories will be.  Not only will we remember the details more easily, but we may think about what we saw more often and even struggle to turn away from it.

Symptoms of post-traumatic stress such as difficulty sleeping, nightmares, and intrusive thoughts can also be stirred by violent programs.  According to one study, 17 percent of the U.S. population outside New York City reported post-traumatic stress symptoms two months after the Sept. 11 attack.  In another study, those who watched 12 or more hours of news coverage of the attack's anniversary were three times more likely to show signs of new post-traumatic stress symptoms.

But you can reduce the negative effects of media violence with these steps:

Reduce exposure through mindfulness practice.  According to research, some people are more strongly attracted to programs that promise violence, but rate those programs as less enjoyable.  This suggests the value in mindfully tracking our internal reactions to what we're watching.   Observing what we feel moment-to-moment could help us realize we would like to separate ourselves from upsetting content.

Consider the potential stress-related effects before watching a violent program.  Simply thinking about the research on the negative effects from viewing could make you more likely to make a different, healthier choice.

Choose something exciting and positive to do, instead.  Substituting an equally stimulating, but more positive, activity, such as exercising, could satisfy the craving for heightened arousal.

Explore your ethical and personal values.  Discussing or writing about ethical and personal values that run counter to engagement with violent media may increase motivation to choose other activities.  Consider practicing meditations that can further cultivate compassion for others, a sense of social responsibility, and distaste for violent content.

More research is needed to understand the best ways to combat the negative influences of media violence; however, each individual step may help reverse a larger public tide of violence attraction.

Scott Glassman, Psy.D., directs "A Happier You," a positive psychology group program at Philadelphia College of Osteopathic Medicine.