There has been a lot of speculation about whether Jared Lee Loughner, the man arrested for the Arizona shooting, has a severe mental illness. But is mental illness a sufficient explanation for his actions? Recent research has found that mental illness is, in fact, tied to an increased risk of violence—but it is not a simple relationship.
Most experts before the 1990s argued that violence perpetrated by the mentally ill was no more common than violence by the non-mentally ill, once socioeconomic factors were taken into account. This view was advocated by several generations of clinicians and mental health workers—perhaps in part to counter the stigma that psychiatric patients were dangerous—but it lacked any consistent evidence.
We now know that there is an increased risk of violence in individuals suffering from severe mental illness. This conclusion has been confirmed by large-scale historical studies drawing on routinely collected national data in Sweden, Denmark, Australia and Finland. These have consistently found an increased risk of violence in individuals with schizophrenia, bipolar disorder and some forms of severe brain injury.
With the advent of new research tools over the past 20 years, more sophisticated summaries of existing studies have also been possible. The most recent systematic review on this subject, published in the journal PLoS Medicine in 2009 and involving over 18,000 subjects in 11 countries, found that individuals with schizophrenia were more likely, as compared to the general public, to commit acts of violence, regardless of how violence was measured. This increase was typically two to five times higher in men with schizophrenia and over four-fold higher in women with schizophrenia. As one expert commented, clinicians have to face up to this “unpalatable” evidence “for the sake of our patients.” A similar review on bipolar disorder and violence from 2010 found similar increases in risk.
These investigations also found, however, that only 3% to 10% of all violence in society is committed by individuals with severe mental illness. In other words, at least 90% of all violent crime in Western countries is committed by people who are not suffering from such conditions. In Sweden, for example, from 1988 to 2000, there were 45 violent crimes per 1,000 persons, of which two to three were attributable to persons with severe mental illness.
Moreover, the vast majority of patients with severe mental illness are not violent during their lifetimes. The largest and longest study of schizophrenia and violence, conducted in Sweden over the course of 30 years, found that only 13% of patients had violent convictions after receiving their diagnoses. For most patients, the risk of becoming a victim of violence is higher than the risk that they will commit violence.
Nor should we make the mistake of assuming that a correlation between mental illness and violence somehow establishes a causal connection between them. It may be that schizophrenia is simply a marker for other factors that increase the risk of violence. Of these factors, one of the strongest is alcohol and drug abuse. Estimates from the U.S. indicate that around half of patients with schizophrenia also have problems with substance abuse. One study in American urban centers found that nearly a third of patients who were discharged from the hospital and also diagnosed with substance abuse were violent within one year…….
Reported by Seena Fazel
The Wall Street Journal
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