Yet surprisingly little population-level evidence supports the notion that individuals with mental illness are more likely than anyone else to commit gun crimes. According to psychiatrist Paul Appelbaum,8 fewer than 3% to 5% of American crimes involve people with mental illness, and the percentages of crimes that involve guns are lower than the national average for persons without a diagnosis of mental illness. Databases that track gun homicides, such as the National Center for Health Statistics, similarly show that fewer than 5% of the 120,000 gun-related killings in the US between 2001 and 2010 were perpetrated by people with mental illness.9
Moreover, a growing body of research suggests that mass shootings represent anecdotal distortions of, rather than representations of, the actions of “mentally ill” people as an aggregate group. By most estimates, there were fewer than 100 mass shootings reported in the US—defined as crimes “when four or more people are shot in an event, or related series of events”—between 1982 and 2012.10 Rates of reported mass shootings rose in 2013 and 2014.
Scholars who study violence prevention contend that mass shootings occur far too infrequently to allow for statistical modeling and predictability—factors that lie at the heart of effective public health interventions. Psychologist Jeffrey Swanson11 argues that mass shootings denote “rare acts of violence” that have little predictive or preventive validity in relation to the bigger picture of the 32,000 fatalities and 74,000 injuries caused on average by gun violence and gun suicide each year in the US.
Links between mental illness and other types of violence are similarly contentious among researchers who study such trends. Study findings suggest that subgroups of persons with severe or untreated mental illness might be at increased risk for violence during periods surrounding psychotic episodes or psychiatric hospitalizations.12 At the same time, a number of seminal studies asserting links between violence and mental illness have been critiqued for overstating connections between serious mental illness and violent acts.13
Media reports often assume a binary between mild and severe mental illness, and they connect the latter form to unpredictability and lack of self-control. However, this distinction is called into question by mental health research. To be sure, a number of the most common psychiatric diagnoses, including depressive, anxiety, and attention-deficit disorders, have no correlation with violence whatsoever. Community studies find that serious mental illness without substance abuse is also “statistically unrelated” to community violence. At the aggregate level, the vast majority of people with psychiatric disorders do not commit violent acts—only about 4% of violence in the US is attributable to persons with mental illness.14
This is not to suggest that researchers know nothing about predictive factors for gun violence. However, credible studies suggest that a number of risk factors more strongly correlate with gun violence than mental illness alone. For instance, alcohol and drug use increase the risk of violent crime by as much as 7-fold, even among persons with no history of mental illness—a concerning statistic in the face of recent legislation that allows persons in certain states to bring loaded handguns into bars and nightclubs. According to Van Dorn and colleagues,15 male sex and a history of childhood abuse and binge drinking are all predictive risk factors for serious violence. Belying Lott’s16 argument that “more guns” lead to “less crime,” Miller and colleagues17 found that homicide was more common in areas in which household firearms ownership was higher. The rate of interpersonal conflicts resolved by fatal shootings jumped by 200% after Florida passed “stand your ground” in 2005.18 The availability of guns is also considered a more predictive factor than is psychiatric diagnosis in many of the 19,000 completed suicides by gun each year in the US.
Some persons with mental illness undoubtedly commit violent acts. Yet growing evidence suggests that mass shootings on which gun legislation is often based represent statistical aberrations that reveal more about particularly horrible instances than they do about population-level events. To use Swanson’s11 phrasing, basing gun-crime prevention efforts on the mental health histories of mass shooters risks building “common evidence” from “uncommon things.” This type of approach loses the opportunity to build common evidence from common things—such as the types of evidence that clinicians of many medical specialties might catalogue, in alliance with communities, about substance abuse, domestic violence, availability of firearms, suicidality, social networks, economic stress, and other factors.
Assumption 2: psychiatric diagnosis can predict gun crime before it happens
Legislation in a number of states mandates that psychiatrists assess their patients for the potential to commit violent gun crime. History suggests, however, that psychiatrists are inefficient gatekeepers in this regard. Data that support the predictive value of psychiatric diagnosis in matters of gun violence are thin at best. Psychiatric diagnosis is largely an observational tool, not an extrapolative one. Largely for this reason, research dating back to the 1970s suggests that psychiatrists using clinical judgment have difficulty in predicting which patients will commit a violent crime.
Dr Metzl is Frederick B. Rentschler II Professor of Sociology and Medicine, Health, and Society; Director of the Center for Medicine, Health, and Society; and Professor of Psychiatry at Vanderbilt University in Nashville, Tenn. He reports no conflicts of interest concerning the subject matter of this article.
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