In the aftermath of the shooting of Rep. Gabrielle Giffords and 19 others at a Tucson supermarket, one overarching question has emerged: Is violent political rhetoric to blame?
Many have argued that warlike words contributed to the actions of Jared Lee Loughner, the 22-year-old man who allegedly killed six people and wounded 14 others, including Giffords (D-Ariz.), on Saturday. Loughner's behavior and online postings suggest that he may have a mental illness, although he has not been officially diagnosed.
Pima County Sheriff Clarence Dupnik kicked off the debate at a news briefing after the shooting, saying that Arizona had become a "capital" for vitriol, prejudice and bigotry. Giffords herself decried violent rhetoric during the last election, when Sarah Palin's political action committee posted a map with what appeared to be the cross-hairs of a gun sight over Gifford's district. (SarahPAC has since removed the image, and a spokesman has said the icons were not meant to be gun sights.)
Can violent political rhetoric push a mentally unstable person over the edge? The answer isn't as simple as yes or no, psychologists say. Violent rhetoric can make people more comfortable with the idea of violence, according to some research, but it's almost impossible to pin down the larger causes of one specific incident, researchers say.
The need for nuance
Debate over Loughner's motives has hewed largely along party lines. Conservative politicians and pundits have been quick to dismiss Loughner as a "madman" and a loner without a coherent political policy. On the other hand, those at the liberal end of the spectrum have blamed militaristic political metaphors for creating a dangerous climate.
In many ways, the debate echoes the conversations that took place after the November 2009 Fort Hood shooting, said Peter Ditto, a psychologist at the University of California, Irvine, who studies political reasoning. In that case, U.S. Army Maj. Nidal Malik Hasan was charged with gunning down 13 people and wounding 30 others.
"In that case, it was the right that's saying, 'This guy did it, this was caused by jihadist motivation,' and the left was saying, 'Oh, you know, he was just crazy,'" Ditto told LiveScience. "So, that was a perfect example of the sort of mirror-image phenomenon."
Neither narrative — "just crazy" or "driven to violent action"— really fits, psychologists say. People with severe mental illnesses are more likely than the general public to commit violent crime, said Seena Fazel, a senior lecturer in psychiatry at the University of Oxford. But that doesn't mean people with severe mental illnesses are automatically dangerous.
"The vast majority of violent crimes in society, including homicides, are not committed by people with mental illness. That needs to be clear," Fazel told LiveScience. "Most people with mental illness are not violent, and most violent crimes are not committed by people who are mentally ill."
Illness and violence
People with acute mental disorders like schizophrenia or bipolar disorder are two to three times more likely to commit violent crimes (not just homicide) than people without mental illness, Fazel's research has found. But there's an important caveat: Substance abuse dramatically increases the risk of violence, up to about eight to 10 times the rate of the general population.
Substance abusers without mental illness have similarly high rates of violence, Fazel said. In other words, saddling the 1 percent of people with schizophrenia with a stigma of violence isn't appropriate, Fazel said, given the much larger numbers of substance abusers in the population.
"If I were to address violence in society, really my one group to target would be the individuals with drug and alcohol problems, irrespective of whether they had an underlying severe mental illness," Fazel said.
Homicides by mentally ill strangers get a lot of attention, but they're rare. A 2009 study published in Schizophrenia Bulletin looked at stranger homicides in Australia, Finland, the Netherlands and Canada and found that there is one case of mentally ill stranger homicide per every 14.3 million people each year. That vanishingly small risk becomes even smaller when mental illness is treated: About 64 percent of the offenders in the study had never received treatment.
A label like "schizophrenic" tells you little about a person, particularly about how violent they might be, said Gordon Paul, a clinical psychologist at the University of Houston. (Paul was not involved in the homicide study.)
"Statistically, people who carry the label of schizophrenia are generally more often victims than they are perpetuators of violence," Paul told LiveScience.
No easy answers
When a mentally ill person does commit a violent act, attributing it to a particular outside influence is difficult. People with mental illnesses are influenced by their environments, Paul said, and can be vulnerable to extremist rhetoric.
"Certainly people who fit the pattern of having relatively low levels of social skills, often times being more withdrawn, are more likely to respond to extremist language on radio, television and that sort of thing," Paul said. "If you look at the history of cult development, that's very often where they get their recruits."
That's good reason to tone it down, Paul said. Still, there hasn't been any systematic research on whether rhetoric pushes people on the edge of sanity off the cliff. The phenomenon is so rare that it would be difficult to get good data, researchers say.
"Whether [demonizing political language] causes somebody to act in some way is really a complicated one," Ditto said. "You're never going to get science to speak to whether some sort of violent political rhetoric caused this particular individual to shoot at the congresswoman."
More generally, research suggests that exposure to violent images and words does increase aggression, said Christopher Federico, a psychologist at the University of Minnesota who studies political attitudes.
Most of these studies are on general media violence, not political phrasing. But a recent study by University of Michigan researchers, yet unpublished, found that overall, watching a political ad with violent words (such as "fight for you" instead of "work for you") did little to change people's opinions on whether political violence could be justified. However, people who saw the violently worded ads who were already high in aggression became more accepting of the idea of political violence.
The country is witnessing an upswing in violent political rhetoric, Federico said. But does the political ad study suggest we can expect more actual violence from those already predisposed?
Again, there are no easy answers, Federico said. "To agree with an abstract question [about political violence], that is something very different than going and emptying a loaded gun into a public place."
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You can follow LiveScience Senior Writer Stephanie Pappas on Twitter @sipappas.