New Yorker: Is There a Link Between Mental Health and Gun Violence?

Swanson's original study is the most widely cited study based on populations outside of institutions. Institutional studies (from prisons and mental hospitals) report higher rates...likely because such environments promote patient perceptions of personal risk and because of enhanced reporting which focuses on behavioral infractions).

At any rate, consideration of Swanson's work once again emerges from the shadows...

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http://www.newyorker.com/science/maria-konnikova/almost-link-mental-health-gun-violence

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Jeffrey Swanson, a medical sociologist and professor of psychiatry at Duke University, first became interested in the perceived intersection of violence and mental illness while working at the University of Texas Medical Branch at Galveston in the mid-eighties...

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In general, we seem to believe that violent behavior is connected to mental illness. And if the behavior is sensationally violent—as in mass shootings—the perpetrator must certainly have been sick. As recently as 2013, almost forty-six per cent of respondents to a national survey said that people with mental illness were more dangerous than other people. According to two recent Gallup polls, from 2011 and 2013, more people believe that mass shootings result from a failure of the mental-health system than from easy access to guns. Eighty per cent of the population believes that mental illness is at least partially to blame for such incidents.

That belief has shaped our politics. The 1968 Gun Control Act prohibited anyone who had ever been committed to a mental hospital or had been “adjudicated as a mental defective” from purchasing firearms. That prohibition was reaffirmed, in 1993, by the Brady Handgun Violence Prevention Act. It has only become more strictly enforced in the intervening years, with the passing of the National Instant Criminal Background Check System Improvement Act, in 2008, as well as by statewide initiatives. In 2013, New York passed the Safe Act, which mandated that mental-health professionals file reports on patients “likely to engage in conduct that would result in harm to self or others”; those patients, who now number more than thirty-four thousand, have had their guns seized and have been prevented from buying new ones.

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When Swanson first analyzed the ostensible connection between violence and mental illness, looking at more than ten thousand individuals (both mentally ill and healthy) during the course of one year, he found that serious mental illness alone was a risk factor for violence—from minor incidents, like shoving, to armed assault—in only four per cent of cases. That is, if you took all of the incidents of violence reported among the people in the survey, mental illness alone could explain only four per cent of the incidents. When Swanson broke the samples down by demographics, he found that the occurrence of violence was more closely associated with whether someone was male, poor, and abusing either alcohol or drugs—and that those three factors alone could predict violent behavior with or without any sign of mental illness. If someone fit all three of those categories, the likelihood of them committing a violent act was high, even if they weren’t also mentally ill. If someone fit none, then mental illness was highly unlikely to be predictive of violence. “That study debunked two myths,” Swanson said. “One: people with mental illness are all dangerous. Well, the vast majority are not. And the other myth: that there’s no connection at all. There is one. It’s quite small, but it’s not completely nonexistent.”

In 2002, Swanson repeated his study over the course of the year, tracking eight hundred people in four states who were being treated for either psychosis or a major mood disorder (the most severe forms of mental illness). The number who committed a violent act that year, he found, was thirteen per cent. But the likelihood was dependent on whether they were unemployed, poor, living in disadvantaged communities, using drugs or alcohol, and had suffered from “violent victimization” during a part of their lives. The association was a cumulative one: take away all of these factors and the risk fell to two per cent, which is the same risk as found in the general population. Add one, and the risk remained low. Add two, and the risk doubled, at the least. Add three, and the risk of violence rose to thirty per cent.

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