Monday, March 15, 2010

Schizophrenia and Violent Crime

A short summary of the latest longitudinal study on the relation of schizophrenia and crime. The entire article is available here.

Associate Professor Niklas Långström

Schizophrenia, Substance Abuse, and Violent Crime

Seena Fazel, MD
Niklas La°ngström, MD, PhD
Anders Hjern, PhD
Martin Grann, PhD
Paul Lichtenstein, PhD

JAMA, May 20, 2009—Vol 301, No. 19
©2009 American Medical Association. All rights reserved.

More than 20 epidemiological studies have reported on the association between major mental disorder and violence, including more than 10 that specifically have examined the relationship with schizophrenia. These reports typically find that schizophrenia is related to a 4- to 6-fold increased risk of violent behavior, which has led to the view that schizophrenia and other major mental disorders are preventable causes of violence
and violent crime.

However, uncertainties remain regarding the reported link.

First, there are wide variations in risk estimates. Second, there is considerable uncertainty whether schizophrenia without substance abuse comorbidity is actually associated with violence. Third, the possible contribution of genetic and early environmental factors in mediating the link between schizophrenia and violence has not been reliably studied.

Conceptual models of violence in schizophrenia postulate that patients with schizophrenia are violent as a consequence of the psychopathologic symptoms of the disorder itself (eg, delusions, hallucinations11) or secondary to comorbid substance use (an established risk factor for violence12).

An alternative model is that schizophrenia and violent behavior co-occur because of familial factors (genetic or early environmental) that are related to both (eg, personality traits such as irritability, poor anger management, or inadequate coping with stress)

If, as we hypothesize, the association of schizophrenia and violence disappears when substance abuse is accounted for and appropriate adjustments are made for confounding, this would suggest that assessment
and treatment for substance abuse comorbidity should be prioritized in individuals deemed at risk. It would
also explain why attempts to find psychotic symptoms associated with violence have produced contradictory results.

Therefore, by using longitudinal designs, we examined the relationship of schizophrenia with violent crime in Sweden from 1973 until 2006.

Our study has 2main findings. First, the association between schizophrenia and violent crime is minimal unless
the patient is also diagnosed as having substance abuse comorbidity.

Whether it is necessary to assess violence risk in all patients, as recommended in the current guidelines of the American Psychiatric Association with “substantial clinical confidence,” the highest category of evidence, will depend on a variety of individual and local factors, including service provision.

On the other hand, our data concur with the importance of effective psychiatric treatment from a public health perspective and the importance of evidence based prevention strategies for dealing with substance abuse.

The second main finding is the variation in violence risk depending on the degree of relatedness between the patient and the control group.

Compared with unrelated general population controls, the risk of violent crime in individuals with schizophrenia and substance abuse comorbidity was increased 4-fold (OR, 4.4; 95% CI, 3.9-5.0). However, unaffected siblings had increased rates of substance abuse compared with unrelated general population controls, which meant that the risk increase for schizophrenia with substance abuse comorbidity compared with these siblings was substantially reduced (OR, 1.8; 95% CI, 1.4-2.4), suggesting familial confounding of this association. Familial confounding may occur through genetic susceptibility or early environmental effects.

In summary, we used longitudinal designs to investigate the risk of violent crime in patients with schizophrenia.Our study substantially increases the evidence base by including more individuals with schizophrenia than the previous studies combined and more precise methods to handle confounding. We demonstrate that the risk of violent crime in schizophrenia in patients without co-morbid substance abuse is only slightly increased. In contrast, the risk is substantially increased among patients with comorbidity and suggests that current practice for violence risk assessment and management in schizophrenia may need review.

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