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….
…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.